Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper for easy cleanup.
Wash the asparagus and trim away the tough, woody ends, then spread the spears out in a single layer on one side of the baking sheet.
Pat the salmon fillet completely dry with a paper towel and place it on the other side of the baking sheet.
In a small bowl, whisk together the olive oil, lemon juice, finely chopped parsley, dill, garlic powder, sea salt, and black pepper.
Drizzle half of the herb oil over the asparagus, tossing to coat evenly, and brush the remaining half generously over the top of the salmon.
Roast in the center of the oven for 12 to 15 minutes, or until the salmon is opaque and flakes easily with a fork and the asparagus is tender.
Serve immediately with an extra squeeze of fresh lemon if desired.