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 bottom ends, then place the spears on one side of the prepared baking sheet.
Place the salmon fillet on the other side of the baking sheet, ensuring there is enough space for heat to circulate.
Drizzle the olive oil evenly over both the salmon and the asparagus spears.
Season everything with the sea salt, black pepper, and garlic powder, tossing the asparagus slightly to ensure even coating.
Thinly slice half of the lemon and layer the rounds directly onto the salmon fillet, then sprinkle half of the fresh dill over the top.
Bake 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.
Squeeze the remaining lemon juice over the dish and garnish with the remaining fresh dill before serving immediately.