Preheat your oven to 400°F (200°C) and line a large baking sheet with parchment paper.
Finely mince the fresh parsley, fresh dill, and garlic clove.
In a small bowl, whisk together the Dijon mustard, lemon juice, minced garlic, and chopped herbs to create a thick paste.
Trim the woody ends off the asparagus and place the spears on one side of the baking sheet.
Drizzle the asparagus with olive oil and season with half of the sea salt and black pepper, tossing to coat evenly.
Place the salmon fillet on the other side of the baking sheet and season with the remaining salt and pepper.
Spread the herb-mustard mixture generously over the top of the salmon, pressing it down to form a crust.
Roast in the oven for 12 to 15 minutes, or until the salmon flakes easily with a fork and the asparagus is tender-crisp.
Serve immediately, garnishing with an extra squeeze of lemon if desired.