Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper.
Snap off the woody ends of the asparagus and place the spears on one side of the prepared baking sheet.
Drizzle the asparagus with half of the olive oil and a pinch of the sea salt and black pepper, tossing to coat evenly.
In a small bowl, whisk together the remaining olive oil, Dijon mustard, minced garlic, finely chopped parsley, and finely chopped dill to create a thick 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 paste evenly over the top of the salmon fillet, pressing it down slightly to adhere.
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.
Remove from the oven and immediately squeeze the fresh lemon juice over both the salmon and the asparagus before serving.