Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper.
Pat the salmon fillet dry with a paper towel and place it on one side of the prepared baking sheet.
In a small mixing bowl, whisk together the Dijon mustard, half of the olive oil, lemon juice, dried parsley, dried dill, and garlic powder until a thick paste forms.
Spread the herb-mustard mixture evenly over the top of the salmon fillet, pressing it down slightly to adhere.
Place the asparagus on the empty side of the baking sheet, drizzle with the remaining olive oil, and sprinkle with the sea salt and black pepper.
Toss the asparagus to coat evenly and spread them out into a single layer.
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-crisp.