Roast Salmon With Leeks and Onions

The smell of roasted leeks has a way of sneaking up on you, sweet and earthy all at once. I started making this salmon dish on weeknights when I needed something satisfying but couldn't face another pile of dishes. The whole thing happens on one pan, which means I actually have time to sit down and eat while it's still hot. There's something about the way the onions caramelize around the edges and the parsley dressing cuts through the richness that makes it feel like more effort than it actually is.

I made this for my sister the first time she visited after moving across the country, and she kept going back for more of that dressing. We ended up spooning it over everything on the plate, even the lemon slices. She texted me two days later asking for the recipe, which is how I knew it was a keeper. Now it's become our unofficial reunion meal, the thing I make when we finally get time together again.

Ingredients

• Salmon fillets, skin-on: Keeping the skin on helps the fish stay moist and gives you a little buffer against overcooking, plus it crisps up nicely against the hot pan.
• Leeks: They turn tender and sweet in the oven, almost melting into the onions, and their mild flavor never fights with the salmon.
• Red onion: The wedges get caramelized edges and a slight bite that balances all the richness on the plate.
• Olive oil: Use it generously on the vegetables so they roast instead of steam, and save the good extra-virgin stuff for the dressing.
• Lemon slices: They roast right on top of the salmon, releasing their juice and perfuming everything underneath.
• Fresh flat-leaf parsley: The backbone of the dressing, it needs to be fresh and finely chopped so every spoonful is bright and green.
• Dijon mustard: Just a touch gives the dressing body and a subtle sharpness that ties the garlic and lemon together.
• Capers: Chop them up small so their briny pop gets distributed evenly, adding little bursts of salt and tang.

Instructions

Preheat and prep:

Set your oven to 400°F and give it time to come up to temperature while you slice the vegetables. A properly hot oven is what gives the leeks and onions those caramelized edges.

Start the vegetables:

Spread the leeks and onion wedges in a single layer on your baking sheet, drizzle with olive oil, season with salt and pepper, and toss everything with your hands to coat evenly. Roast them alone for 10 minutes so they get a head start on the salmon.

Add the salmon:

Pull the pan out and tuck the salmon fillets skin-side down right into the vegetables, then lay lemon slices over the top. The vegetables will cushion the fish and keep it from drying out.

Finish roasting:

Slide everything back into the oven for 12 to 15 minutes, until the salmon is just cooked through and flakes easily. The leeks should be soft and starting to brown at the tips.

Make the dressing:

While the salmon roasts, stir together the parsley, garlic, mustard, capers, lemon zest, olive oil, and lemon juice in a small bowl. Taste it and adjust the salt and pepper until it sings.

Plate and serve:

Transfer the salmon and vegetables to plates and spoon the parsley dressing generously over the top. Serve it right away while everything is still hot and the dressing is cool and fresh.

Save

There was one night I made this after a particularly long day, and I remember standing at the counter eating straight off the baking sheet because I didn't want to wait. The parsley dressing pooled around the vegetables and I kept dragging bites of salmon through it, too tired to care about plating. It tasted perfect anyway, which reminded me that good food doesn't need ceremony, just honest flavors and a moment to enjoy them.

Choosing Your Salmon

Look for fillets that are similar in thickness so they cook evenly, and don't be afraid to ask the fishmonger to portion them for you. If the skin looks shiny and the flesh springs back when you press it gently, you're in good shape. I usually go for wild-caught when I can find it, but farmed salmon works just fine here and tends to be a little fattier, which keeps it moist.

Getting the Dressing Right

The dressing should taste bold on its own because it's going to mellow out when it hits the warm salmon and vegetables. If it feels too sharp, add a tiny drizzle more olive oil. If it's flat, a pinch of salt or an extra squeeze of lemon will wake it up. I like to make it right before serving so the parsley stays vibrant and doesn't turn dark.

Serving Suggestions and Swaps

This dish plays well with almost any simple side, roasted potatoes, steamed rice, or even crusty bread to soak up the dressing. If you can't find leeks, use a couple of halved fennel bulbs or thick slices of zucchini. Trout or cod will work in place of salmon, just adjust the cooking time since they're often thinner.

• Add a pinch of crushed red pepper flakes to the dressing if you like a little heat.
• Swap the red onion for shallots if you want something milder and sweeter.
• Leftovers reheat surprisingly well, just add a fresh squeeze of lemon before serving.

Save

This is the kind of recipe that makes weeknight cooking feel less like a chore and more like taking care of yourself. I hope it becomes one of those dishes you reach for when you need something good without the fuss.

Recipe FAQs

→ Can I use frozen salmon fillets?

Yes, but ensure they are completely thawed and patted dry before roasting to achieve the best texture and even cooking.

→ What can I substitute for leeks?

You can use thinly sliced fennel bulbs or additional red onions if leeks are unavailable. Shallots also work wonderfully.

→ How do I know when the salmon is cooked through?

The salmon is ready when it flakes easily with a fork and reaches an internal temperature of 145°F. The flesh should be opaque throughout.

→ Can I make the parsley dressing ahead of time?

Absolutely. Prepare the dressing up to 24 hours in advance and store it covered in the refrigerator. Stir well before serving.

→ What other fish work well with this method?

Trout, Arctic char, cod, or halibut are excellent alternatives. Adjust cooking time based on the thickness of your fish fillets.

→ Can I add other vegetables to the pan?

Yes, cherry tomatoes, bell peppers, or asparagus make great additions. Just ensure they're cut to similar sizes for even roasting.