Prepare Oven and Pan: Adjust your oven rack to the middle position and preheat to 400°F (205°C). Line a large, rimmed baking sheet with parchment paper for easy cleanup.

Mix Lemon-Herb Dressing: In a small bowl, vigorously whisk together the avocado oil (or olive oil), fresh lemon juice, minced garlic, chopped fresh dill, sea salt, and black pepper until well combined. Measure out and reserve 1 ½ tablespoons of this dressing; set it aside for the green vegetables.

Marinate Salmon: Place the salmon fillets in a shallow dish or a resealable bag. Pour about half of the unreserved dressing over the salmon, ensuring the fillets are lightly coated. Allow the salmon to marinate in the refrigerator while you prepare the vegetables.

Prepare Sweet Potatoes: Wash, peel, and slice the sweet potato into thin rounds (approximately ⅛-inch thick). Transfer the sweet potato slices to the prepared baking sheet. Drizzle the remaining portion of the unreserved dressing over the sweet potatoes. Toss gently to ensure even coating, then arrange them in a single layer on one side of the baking sheet.

First Bake (Sweet Potatoes): Place the baking sheet with the sweet potatoes into the preheated oven. Bake for 12-14 minutes, or until they begin to soften.

Add Green Vegetables: Carefully remove the baking sheet from the oven. Push the sweet potatoes to one side. Add the trimmed green beans, asparagus spears, and sliced red onion to the empty space on the baking sheet. Drizzle the reserved 1 ½ tablespoons of dressing over these new vegetables and toss them lightly to coat. Spread them in an even layer.

Second Bake (Vegetables): Return the baking sheet to the oven and bake for an additional 6-8 minutes, until the green beans and asparagus are tender-crisp.

Add Salmon and Finish Baking: Once more, remove the baking sheet from the oven. Create space in the center of the pan, nestled amongst the vegetables, for the marinated salmon fillets. Place the salmon fillets skin-side down (if using skin-on). Top each fillet with a thin slice or two of lemon.

Final Bake (All Components): Return the baking sheet to the oven. Bake for 12-18 minutes, or until the salmon is cooked through and flakes easily with a fork, and its internal temperature reaches 135-140°F (57-60°C) for medium doneness. The sweet potatoes should be fully tender, and the green beans and asparagus should be vibrant and tender-crisp.

Serve: Carefully remove the sheet pan from the oven. Serve the salmon and roasted vegetables immediately.