Roast Salmon With Leeks and Onions

The smell of caramelized onions always pulls me back into the kitchen, even when I'm trying to relax. I started making this salmon dish on a Thursday night when I had exactly one clean pan left and a fridge full of vegetables that needed attention. The leeks were softer than I expected, the salmon crisped beautifully, and the parsley dressing brought everything to life in a way I didn't anticipate. It became my answer to those evenings when I wanted something nourishing without the usual pile of dishes. Now it's the dish I turn to when I need dinner to feel effortless and special at the same time.

I made this for my sister the first time she visited after moving across the country. She walked into the kitchen while the leeks were roasting and said it smelled like comfort, which felt exactly right. We ate at the counter with the pan still warm between us, spooning extra dressing over everything. She asked for the recipe before she even finished her plate, and I knew it had passed some unspoken test.

Ingredients

• Salmon fillets: Skin-on fillets hold together better during roasting and give you a chance at crispy skin if your oven runs hot.
• Leeks: They soften beautifully and turn almost sweet when roasted, but make sure to rinse them well because grit hides between the layers.
• Red onion: The wedges caramelize at the edges and add a mild sweetness that balances the richness of the fish.
• Olive oil: Use a good one for drizzling over the vegetables so they roast evenly and don't stick to the pan.
• Lemon slices: They sit on top of the salmon and release just enough acidity to keep everything bright.
• Fresh flat-leaf parsley: The backbone of the dressing, it should be vibrant green and smell grassy when you chop it.
• Garlic clove: One small clove is enough to give the dressing a gentle bite without overwhelming the herbs.
• Dijon mustard: It adds sharpness and helps the dressing cling to the salmon instead of sliding off.
• Capers: These little bursts of brine make the dressing feel complex and a little fancy.
• Lemon zest and juice: Fresh citrus wakes everything up and ties the whole dish together.

Instructions

Preheat and Prep:

Set your oven to 400°F and give it time to fully heat while you slice the vegetables. A hot oven ensures the leeks and onions start caramelizing right away instead of steaming.

Roast the Vegetables:

Spread the leeks and onion wedges across a large baking sheet, drizzle with olive oil, season with salt and pepper, and toss until everything glistens. Roast them alone for 10 minutes so they get a head start on softening.

Add the Salmon:

Pull the sheet out and tuck the salmon fillets skin-side down among the vegetables, then lay lemon slices on top. Return it to the oven and roast for 12 to 15 minutes until the salmon flakes easily and the vegetables are tender.

Make the Dressing:

While the salmon bakes, chop the parsley finely and mix it with garlic, mustard, capers, lemon zest, olive oil, and lemon juice in a small bowl. Taste it and adjust the salt and pepper until it feels balanced.

Serve:

Plate the salmon and vegetables together, then spoon the parsley dressing generously over the top. Serve it immediately while everything is still warm and the dressing is bright.

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There's something about pulling a single pan out of the oven and knowing dinner is completely done. No sauté pan to scrub, no pot of water to drain, just roasted vegetables and perfectly cooked fish that smell like you spent hours in the kitchen. It's the kind of meal that makes you feel capable and calm at the same time.

How to Pick the Best Salmon

Look for fillets that are firm to the touch and smell like the ocean, not fishy or strong. The flesh should be bright and slightly translucent, and if you're buying skin-on, the skin should look shiny and intact. I always ask the fishmonger what came in that day instead of defaulting to what's on display, and it's made a noticeable difference in how the salmon tastes.

Getting the Most Out of Leeks

Leeks hold onto dirt like it's their job, so slice them first and then rinse the rounds in a bowl of cold water, swishing them around until the grit settles to the bottom. I learned this after biting into a sandy piece during an otherwise perfect dinner, and now I never skip it. When they roast, they become tender and almost buttery, so give them enough space on the pan to caramelize instead of crowding them together.

Making the Dressing Shine

The parsley dressing is what makes this dish feel special, so don't be shy with the herbs or the lemon. I like to chop the parsley by hand instead of using a food processor because it stays brighter and doesn't turn into a paste. If you want a little heat, add a pinch of crushed red pepper flakes, and if you love garlic, go ahead and use a full clove instead of a small one.

• Taste the dressing before serving and adjust the lemon juice or salt to your preference.
• If you have leftover dressing, it's excellent on roasted potatoes or spooned over grilled chicken.
• Make it up to an hour ahead and let it sit at room temperature so the flavors meld together.

Save

This is the kind of recipe that makes weeknight cooking feel doable and rewarding instead of rushed and stressful. I hope it becomes one of those dishes you reach for when you want something good without the fuss.

Recipe FAQs

→ Can I use frozen salmon fillets?

Yes, just ensure they are completely thawed and patted dry before roasting to achieve the best texture and prevent excess moisture on the baking sheet.

→ What other vegetables can I add to this dish?

Cherry tomatoes, fennel, asparagus, or bell peppers work beautifully. Add heartier vegetables at the beginning with the leeks, and more delicate ones when you add the salmon.

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

The salmon should flake easily with a fork and reach an internal temperature of 145°F. It should appear opaque throughout with a slightly translucent center if you prefer it medium.

→ Can I prepare the parsley dressing in advance?

Absolutely. The dressing can be made up to 24 hours ahead and refrigerated in an airtight container. Bring to room temperature before serving for best flavor.

→ What can I substitute for capers in the dressing?

Finely chopped green olives or a small amount of pickle relish provide similar briny, tangy notes. You can also simply add an extra squeeze of lemon juice.

→ Is the skin on the salmon necessary?

While not required, skin-on fillets help the salmon hold together during roasting and provide a protective layer. You can easily remove it after cooking if preferred.