Roast Salmon With Leeks Onions

The smell of caramelizing onions hit me before the timer even went off. I was testing this salmon recipe on a Tuesday night, exhausted from work, and I'd honestly forgotten I'd put anything in the oven. When I opened the door, the leeks had turned golden at the edges, the salmon skin was crisping beautifully, and I realized I'd stumbled onto something that required almost no effort but looked like I'd been cooking all day. I ate standing at the counter, straight from the pan, with no regrets.

I made this for friends who claimed they didn't like cooked onions. They devoured the roasted red onion wedges first, then sheepishly asked for the recipe. The high heat transforms them into something sweet and jammy, nothing like the sad, slimy rings they were imagining. Now it's my go-to for converting vegetable skeptics.

Ingredients

• Salmon fillets, skin-on: The skin protects the flesh from drying out and crisps up beautifully if you let it sit undisturbed on the hot pan.
• Leeks: Slice them into thick rounds so they hold their shape and get tender without falling apart.
• Red onion: Wedges work better than thin slices here, they get caramelized edges while staying just slightly firm in the center.
• Olive oil: Don't skimp, it helps the vegetables roast instead of steam.
• Sea salt and black pepper: Simple seasoning lets the natural sweetness of the vegetables shine.
• Lemon slices: They roast right on top of the salmon, infusing it with subtle citrus and looking gorgeous on the plate.
• Fresh flat-leaf parsley: The backbone of the dressing, it should be finely chopped so every bite gets a burst of green freshness.
• Garlic clove: One small clove is enough, you want a whisper of sharpness, not a punch.
• Dijon mustard: Adds body and a hint of tang that ties the dressing together.
• Capers: Briny little bursts that balance the richness of the fish.
• Lemon zest: Use a microplane if you have one, the oils in the zest add incredible fragrance.
• Extra-virgin olive oil: This is a finishing oil, so use something you'd happily drizzle on bread.
• Fresh lemon juice: Squeeze it just before mixing to keep it bright and lively.

Instructions

Get the oven hot:

Preheat to 400°F (200°C). A hot oven is key to getting those caramelized edges on the vegetables.

Prep the vegetables:

Spread the leeks and red onion wedges across a large baking sheet in a single layer, drizzle with olive oil, season with salt and pepper, and toss with your hands to coat everything evenly. Don't crowd the pan or they'll steam instead of roast.

Roast the vegetables first:

Slide the pan into the oven for 10 minutes. This head start ensures the vegetables get tender and golden before the salmon finishes cooking.

Add the salmon:

Pull the pan out, nestle the salmon fillets skin-side down among the vegetables, and lay lemon slices over the top of each fillet. The vegetables cushion the fish and keep it moist.

Finish roasting:

Return the pan to the oven and roast for 12 to 15 minutes, until the salmon is just cooked through and flakes easily with a fork. The skin should be crisp and the vegetables tender with browned edges.

Make the dressing:

While the salmon bakes, combine parsley, garlic, Dijon, capers, lemon zest, olive oil, and lemon juice in a small bowl. Stir well, taste, and adjust salt and pepper as needed.

Plate and dress:

Transfer the salmon and vegetables to plates, spoon the parsley dressing generously over the salmon, and serve immediately. The dressing should pool around the fish, mingling with the roasted juices.

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The first time I served this, my partner looked at the bright green dressing and asked if it was pesto. When I told him it was just parsley, garlic, and lemon, he was stunned. It's become our Sunday night default, the meal we make when we want something nourishing without the fuss. I love how the house smells like roasted lemons and how the pan is clean in under a minute.

Choosing Your Salmon

I've made this with wild-caught sockeye, farmed Atlantic, and even frozen fillets I thawed in the fridge overnight. The cooking time stays the same, but wild salmon tends to be leaner and can dry out faster, so check it at the 12-minute mark. Skin-on is non-negotiable for me, it acts like a protective shield and crisps up so nicely that I sometimes eat it first, like a savory cracker.

Storing and Reheating

Leftovers keep in an airtight container in the fridge for up to two days. I usually don't reheat the salmon, I flake it cold over a salad or toss it with pasta and a little extra dressing. If you do reheat, use a low oven (300°F) and cover it loosely with foil to keep it from drying out. The vegetables reheat beautifully and somehow taste even sweeter the next day.

Swaps and Tweaks

If you can't find leeks, use halved fennel bulbs or thick slices of zucchini. Trout and cod both work well in place of salmon, just adjust the cooking time based on thickness. For a spicier kick, I sometimes add a pinch of crushed red pepper flakes to the dressing or swap half the parsley for cilantro.

• Serve with roasted baby potatoes or a simple grain like farro for a more filling meal.
• A handful of cherry tomatoes added to the pan with the vegetables adds sweetness and juiciness.
• If you're not a fan of capers, try finely chopped green olives instead.

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This is the kind of recipe I come back to when I need dinner to feel effortless but special. It's proof that good food doesn't have to be complicated, just thoughtfully seasoned and cooked with a little attention.

Recipe FAQs

→ Can I use frozen salmon fillets?

Yes, just ensure they're fully thawed and patted dry before roasting to achieve the best texture and even cooking.

→ What can I substitute for leeks?

You can use sliced fennel, shallots, or additional red onion if leeks aren't available. Adjust cooking time as needed for tenderness.

→ 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. It will appear opaque throughout with a slightly pink center.

→ Can I make the parsley dressing ahead?

Absolutely. Prepare the dressing up to 24 hours in advance and store it covered in the refrigerator. Bring to room temperature before serving.

→ What sides pair well with this dish?

This salmon pairs beautifully with roasted potatoes, quinoa, steamed rice, or a simple green salad for a complete, balanced meal.

→ Can I use dried parsley instead of fresh?

Fresh parsley is highly recommended for the dressing's vibrant flavor and texture. Dried parsley won't provide the same fresh, bright taste.