Roast Salmon With Leeks Onions

The smell of roasted leeks hit me before I even opened the oven door. I was testing this recipe on a Wednesday night when I had no energy for dishes, and the whole thing came together on one pan. The salmon came out perfectly tender, the vegetables sweet and charred at the edges. That bright parsley dressing I whisked together while everything roasted became the thing I started putting on just about everything that week.

I made this for my sister when she came over unannounced, hungry and frazzled from a long day. She sat at the counter while I prepped, and we talked over the sound of the knife hitting the cutting board. When I pulled the pan from the oven, she looked at the golden salmon with those lemon slices on top and said it looked like something from a restaurant. It tasted even better than it looked, and she took the leftover dressing home in a jar.

Ingredients

• Salmon fillets, skin-on: Keeping the skin on helps the fish stay moist and prevents it from falling apart on the pan.
• Leeks: They turn sweet and silky when roasted, make sure to rinse them well since dirt hides between the layers.
• Red onion: The wedges soften and pick up a little char, adding depth and a hint of sweetness.
• Olive oil: Used twice, once to coat the vegetables and again in the dressing for richness.
• Lemon slices: They roast right on top of the salmon, infusing it with citrus without any extra effort.
• Fresh flat-leaf parsley: The backbone of the dressing, it brings a grassy brightness that cuts through the richness of the fish.
• Garlic clove: Just one small clove minced fine, it sharpens the dressing without overpowering it.
• Dijon mustard: Adds a subtle tang and helps emulsify the dressing so it clings to the salmon.
• Capers: Salty, briny little bursts that wake up every bite.
• Lemon zest and juice: Zest gives aroma, juice gives acidity, together they make the dressing sing.

Instructions

Get the oven ready:

Preheat your oven to 400°F so it is fully hot when the vegetables go in. This ensures they start caramelizing right away instead of steaming.

Prep and roast the vegetables:

Spread the leeks and red onion on a large baking sheet in a single layer, drizzle with olive oil, season with salt and pepper, and toss with your hands to coat evenly. Roast them for 10 minutes until they start to soften and the edges begin to brown.

Add the salmon:

Pull the pan out and tuck the salmon fillets skin-side down right into the vegetables, then lay lemon slices over each piece. Slide it back into the oven and roast for 12 to 15 minutes until the salmon is just cooked through and flakes easily.

Make the parsley dressing:

While the salmon roasts, combine parsley, garlic, Dijon, capers, lemon zest, olive oil, and lemon juice in a small bowl and stir until it comes together. Taste it and adjust the salt and pepper as needed.

Serve it up:

Transfer the salmon and vegetables to plates, spoon that vibrant green dressing generously over the top, and serve right away while everything is still warm.

Pin it

This became my go-to when I wanted to feel like I had my life together without actually spending hours in the kitchen. One night I served it with nothing but crusty bread to soak up the dressing, and it felt like exactly enough. There is something satisfying about a meal that tastes this bright and looks this pretty but does not leave you with a sink full of pans.

Storing and Reheating

Leftovers keep well in an airtight container in the fridge for up to two days. I usually eat the salmon cold the next day on top of greens with extra dressing, and it is just as good. If you want to reheat it, use a low oven around 300°F for about 10 minutes so the fish does not dry out, and add a little more dressing after warming to freshen it up.

Swaps and Variations

You can easily swap the salmon for trout or even cod if that is what you have on hand, just adjust the cooking time since thinner fillets cook faster. I have also made this with fennel instead of leeks when I found a beautiful bulb at the market, and the anise flavor paired beautifully with the lemon. If you are not a caper person, try chopped green olives instead for that same briny pop.

Serving Suggestions

This dish is light enough on its own, but if you want to make it more filling, serve it alongside roasted baby potatoes or a simple bowl of steamed rice. A crisp white wine or sparkling water with lemon feels right with it. I have also piled everything over a bed of arugula and let the warm salmon wilt the greens slightly, turning it into a warm salad that feels both virtuous and indulgent.

• Serve with crusty bread to mop up every bit of that parsley dressing.
• Add a handful of cherry tomatoes to the pan with the vegetables for extra color and sweetness.
• Garnish with extra lemon wedges and a few whole parsley leaves for a restaurant finish.

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This is the kind of recipe that makes you feel capable and calm, even on nights when you are anything but. I hope it does the same for you.

Recipe FAQs

→ Can I use frozen salmon fillets?

Yes, just ensure they are fully thawed and patted dry before roasting for best results.

→ What can I substitute for leeks?

Use sliced fennel, shallots, or additional onions if leeks are unavailable.

→ How do I know when the salmon is done?

The salmon should flake easily with a fork and reach an internal temperature of 145°F.

→ Can I make the parsley dressing ahead?

Absolutely. Prepare it up to 2 days in advance and store refrigerated in an airtight container.

→ What sides pair well with this dish?

Roasted potatoes, steamed rice, quinoa, or a simple green salad complement the salmon beautifully.

→ Can I use a different type of fish?

Yes, trout, cod, or halibut work well as substitutes with similar cooking times.