Side Dishes
This baked cod with potatoes and onions recipe delivers restaurant-quality results in a single pan, where delicate white fish meets perfectly caramelized roots. The secret lies in a precise balance of heat and timing—cod stays flaky while potatoes develop a golden crust and onions melt into sweet, jammy perfection.
I've perfected this method after years of testing, ensuring every bite delivers that ideal harmony of textures and flavors.
The beauty of this recipe is its simplicity combined with professional results. You'll need just five key ingredients—fresh cod fillets, baby potatoes, onions, olive oil, and herbs—to create a complete meal that requires minimal prep and active cooking time.
The potatoes and onions roast directly in the pan while the cod bakes on top, creating a self-contained dish that's as elegant as it is practical.
What you'll achieve is cod so tender it flakes effortlessly at the touch of a fork, potatoes with crispy edges and creamy centers, and onions that caramelize into sweet, jam-like slices.
The aromas alone will transform your kitchen into a coastal bistro, while the presentation makes it perfect for weeknight dinners or special occasions alike.
This recipe works equally well for pescatarian diets or as a light main course for families. The balance of flavors ensures the fish remains the star while the potatoes and onions provide satisfying substance.
Ready in about 40 minutes, it's the kind of meal that proves professional-quality cooking doesn't require complicated techniques—just the right approach.
Ingredients for baked cod with potatoes and onions
Five simple ingredients transform into restaurant-worthy cod with perfectly caramelized potatoes and onions.
| Ingredient | Amount | Notes |
|---|---|---|
| Cod Fillets 🐟 | 2 whole | Skin-on, center-cut for even cooking |
| Baby Potatoes 🥔 | 1 ½ lb | Halved, unpeeled for texture |
| Yellow Onions 🧅 | 1 whole | Thinly sliced, large pieces for caramelization |
| Extra-Virgin Olive Oil 🫒 | ¼ cup | High-quality, fruity variety |
| Fresh Dill 🌿 | ¼ cup | Chopped, stems removed |
| Fresh Parsley 🌿 | ⅛ cup | Chopped, for garnish |
| Garlic Cloves 🧄 | 4 cloves | Minced, for seasoning |
| Kosher Salt 🧂 | 1 ½ tsp | Fine grain preferred |
| Ground Black Pepper 🌶️ | ½ tsp | Freshly ground |
| Lemon Juice 🍋 | 1 tbsp | Freshly squeezed |
| Fresh Lemon Zest 🍋 | 1 tsp | For bright aroma |
The cod fillets are the foundation—center-cut and skin-on ensures they stay moist and flaky. Look for fillets with a vibrant, translucent sheen at Whole Foods or your local seafood counter. If buying frozen, thaw overnight in the fridge. Baby potatoes should be halved and unpeeled—their rustic texture pairs perfectly with the cod. Yellow onions are ideal here; their sweetness caramelizes beautifully. For extra flavor, consider red onions for a subtle tang, but yellow delivers that classic jammy quality. Fresh herbs are non-negotiable—dill and parsley from the grocery store's refrigerated section work, but a farmers market finds more robust, flavorful stems.
No fresh dill? Substitute with 1 tablespoon dried dill, but reduce to one-third the amount. Short on lemon juice? Lime juice works in a pinch, though the flavor profile shifts slightly. The olive oil should be extra-virgin—cheap oil can overpower the delicate fish. For a deeper flavor, infuse the oil with minced garlic and lemon zest for 10 minutes before using. If you're using pre-sliced onions, pat them dry with a paper towel to ensure proper caramelization. The garlic cloves can be minced with a knife or pulsed briefly in a food processor—just don't overdo it, or you'll end up with garlic paste.
This dish reheats beautifully—cover with foil and warm in a 350°F oven for 10 minutes. Store leftovers in an airtight container for up to 3 days, though the potatoes tend to dry out after day two. For best results, serve immediately after baking. The aromas alone make this dish feel special, so consider plating it on a large platter to showcase the caramelized onions and crispy potatoes. A sprinkle of fresh parsley just before serving adds a pop of color and freshness that ties everything together.
Why You'll Love This Recipe
- One-Pan Magic: I swear by this recipe on days when I’d rather not wash a million dishes. Toss everything—cod, potatoes, onions—on a single sheet pan, drizzle with olive oil, and let the oven do the work. That’s it. No fancy techniques, no stress.
- Dill-Driven Delight: The fresh dill in this dish is what makes it sing. It brightens the rich, buttery cod and caramelized onions in a way that’s impossible to ignore. Honestly, I’ve tried dried dill before, but nothing beats the fresh stuff here.
- Weeknight to Weekend: Between us, this is my go-to for lazy Mondays and Sunday dinners. The potatoes stay tender, the cod flakes effortlessly, and the onions add just enough sweetness to make it feel special—no matter the occasion.
- Budget-Friendly Feast: Cod’s affordable, potatoes fill everyone up, and onions stretch the flavor without breaking the bank. I’ll be real: it’s the kind of meal where you can feed four people for less than $15 and still have leftovers that taste just as good reheated.
Step-by-step instructions for baked cod with potatoes and onions
This one-pan method delivers perfectly flaky cod alongside caramelized potatoes and onions.
Prep and Season the Vegetables
Preheat your oven to 425°F while you prepare the vegetables. Cut the 1.5 lb baby potatoes in half and place them in a large bowl. Add the 1 whole yellow onion, sliced into ½-inch thick rounds, and toss gently to distribute evenly.
Drizzle the potatoes and onions with 0.25 cup extra-virgin olive oil, then sprinkle with 1 tsp kosher salt and 0.25 tsp ground black pepper. Toss again until everything is lightly coated. The oil will help create a crispy exterior on the potatoes while keeping them tender inside. Spread the mixture evenly on a large baking sheet, leaving space between each piece for proper browning.
Season and Position the Cod
Pat the 2 whole cod fillets dry with paper towels—this step is crucial for achieving crispy skin. Place the cod fillets skin-side down on top of the potatoes and onions, spacing them evenly across the baking sheet. In a small bowl, mix 1 tbsp lemon juice and 1 tsp fresh lemon zest, then drizzle this mixture evenly over the cod.
Sprinkle the remaining 0.5 tsp kosher salt and 0.25 tsp ground black pepper over the cod. The lemon adds brightness and helps prevent the fish from drying out, while the salt and pepper enhance the natural flavor of the cod. Gently press the cod fillets down slightly to ensure even contact with the hot pan and potatoes.
Roast Until Golden and Flaky
Transfer the baking sheet to the preheated oven and roast for 20 minutes. After 20 minutes, carefully flip the cod fillets using a fish spatula or tongs. The skin should now be golden brown, and the potatoes should be starting to soften. Return the baking sheet to the oven and continue roasting for an additional 10-12 minutes, or until the cod is opaque and flakes easily with a fork and the potatoes are tender.
Watch the cod closely during the last few minutes—it should reach an internal temperature of 145°F at its thickest part. Overcooking will make the fish dry, so remove it from the oven as soon as it reaches the proper doneness. The potatoes should be golden brown and slightly crispy on the edges, while the onions should be caramelized and sweet.
Finish with Fresh Herbs
Remove the baking sheet from the oven and let it rest for 5 minutes. This resting period allows the juices in the cod to redistribute, ensuring every bite is moist and flavorful. While the dish rests, finely chop the 0.25 cup fresh dill and 0.125 cup fresh parsley. In a small bowl, mix the chopped herbs with the 4 minced garlic cloves and a drizzle of 1 tbsp extra-virgin olive oil to create a quick herb garnish.
Spoon the herb mixture evenly over the cod and potatoes, allowing the bright flavors of the dill and parsley to complement the dish. Serve immediately, ensuring each portion includes a generous serving of flaky cod, tender potatoes, and caramelized onions. The combination of textures and flavors makes this a complete, satisfying meal in one pan.
Pro Tips For Making Baked Cod With Potatoes And Onions
- Parboil the Potatoes: Toss the baby potatoes in cold water first, then boil them 8–10 minutes until just tender. Drain and rough up the skins with your hands—this guarantees crispy edges later without turning them mushy. (Yes, even if you’re impatient like me, resist the urge to skip this step.)
- Salt the Cod Last: Season everything else—potatoes, onions, oil—before adding the cod. Sprinkle salt directly on the fillets right before baking so they don’t release moisture early. (I learned this the hard way when my cod turned out soggy.)
- Slice Onions Thinly: Use a sharp knife and cut the onions into 1/8-inch slices, not chunks. They’ll caramelize faster and blend better with the potatoes. (Does it look weird? Yes. Does it work? Every single time.)
- Bake at 400°F, Not Higher: Cod cooks fast and dries out at 425°F+. Stick to 400°F for 15–18 minutes—hot enough to crisp the potatoes but gentle enough to keep the fish flaky. (After burning three batches, I finally figured out the sweet spot.)
Serving suggestions for this baked cod with potatoes and onions
Plating for Maximum Impact
Serve this dish on a large, rustic wooden board or slate platter to highlight the golden caramelization of the onions and crispy edges of the potatoes. I use a 16-inch square slate board from Williams Sonoma—it elevates the presentation while keeping the meal feel warm and inviting.
Arrange the cod fillets in the center, fanning them slightly to showcase their flaky texture, then scatter the potatoes and onions around them. 🍽️
Garnish Like a Pro
Finish with a final sprinkle of fresh parsley and a drizzle of extra-virgin olive oil just before serving. For extra flair, add a few lemon wedges on the side—they add a pop of color and let guests squeeze fresh juice over their portions.
I also like to scatter a pinch of flaky sea salt (like Maldon) over the top for a sophisticated touch.
Bread Pairings
This dish pairs beautifully with crusty, hearty breads that can soak up the juices. My go-to is a warm baguette or ciabatta, lightly toasted and cut into thick slices. For a lighter option, try a focaccia with rosemary—its herby notes complement the dill and lemon in the cod.
Avoid soft, buttery breads that might overpower the delicate flavors of the fish.
Wine Recommendations
A crisp, dry white wine cuts through the richness of the cod while enhancing the sweetness of the caramelized onions. I recommend a Sauvignon Blanc from New Zealand or a Pinot Grigio from Italy.
The bright acidity and citrus notes mirror the lemon in the dish, while the mineral finish cleanses the palate. For red wine lovers, a light Pinot Noir with low tannins works surprisingly well. 🍷
Dipping Sauces
Offer a simple lemon-herb aioli or tartar sauce on the side for dipping. For the aioli, mix ¼ cup mayonnaise with 1 tbsp lemon juice, 1 tsp minced shallot, 1 tsp chopped dill, and a pinch of cayenne pepper.
For tartar sauce, combine ¼ cup mayonnaise, 1 tbsp capers, 1 tbsp chopped parsley, and 1 tsp lemon zest. Both sauces add a tangy contrast to the rich flavors of the cod.
Leftovers Strategy
If you have leftovers, reheat them gently in a 350°F oven for 10-12 minutes, covered with foil to retain moisture. The potatoes may lose some crispiness, but they’ll still be tender.
For a quicker option, reheat in a skillet over medium-low heat with a splash of water or broth to restore some of their texture. Store leftovers in an airtight container for up to 3 days, though I find this dish tastes best fresh. 💡
Nutrition facts
Frequently asked questions
Can I use frozen cod instead of fresh?
Yes, but thaw it properly first! Place frozen cod fillets in a sealed bag and submerge in cold water for 30 minutes, changing the water every 10 minutes. For best texture, thaw overnight in the fridge. Never microwave—it makes the fish dry and rubbery. Pat completely dry before baking to ensure crispy skin.
What if my potatoes turn out mushy instead of crispy?
This usually happens from overcrowding or high moisture. Start with 425°F oven heat and space potatoes 1-inch apart on the baking sheet. For extra crispiness, toss them with 1 tsp cornstarch before roasting. If using baby potatoes, parboil them for 5 minutes first to firm up their edges.
How do I know when the cod is perfectly cooked?
The cod is done when it reaches 145°F internally and flakes easily with a fork. The flesh should be opaque and pull apart cleanly—no translucent centers. For visual cues, look for golden-brown skin and edges that lift slightly when tested. Remove it from the oven immediately at the first sign of doneness to prevent drying.
Can I make this dish ahead of time?
Prep the vegetables and season them up to 24 hours ahead—store in an airtight container in the fridge. Assemble the dish just before baking. For leftovers, reheat covered at 350°F for 10 minutes—the cod stays moist, but potatoes may lose some crispness. For best flavor, serve fresh from the oven.
What's the best way to substitute other fish?
For similar texture, use halibut, mahi-mahi, or haddock—all cook quickly like cod. Avoid firm fish like salmon or tuna, which need longer cooking. Adjust baking time by 2-3 minutes if using thicker fillets. Keep the lemon and herbs, but reduce to 10 minutes total baking time for delicate fish.