Preheat your oven to 400°F and line a large rimmed baking sheet with parchment paper.
Wash the asparagus and trim away the tough, woody ends, then place them on one side of the baking sheet.
Drizzle the asparagus with the olive oil and season with half of the sea salt and black pepper, tossing to coat evenly.
In a small mixing bowl, combine the Dijon mustard, lemon juice, lemon zest, finely chopped parsley, and dill to create the herb paste.
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 fillet, pressing it down slightly to adhere.
Bake for 12 to 15 minutes, or until the salmon flakes easily with a fork and the asparagus is tender and slightly charred.
Serve immediately with an extra squeeze of fresh lemon if desired.