Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper for easy cleanup.
Trim the tough, woody ends off the asparagus spears and arrange them in a single layer on one side of the prepared baking sheet.
Place the salmon fillet on the other side of the baking sheet, skin-side down.
In a small ramekin, whisk together the olive oil, minced garlic, dried dill, sea salt, and black pepper until well combined.
Drizzle the herb oil mixture over both the salmon and the asparagus, using a brush or your hands to ensure the asparagus is evenly coated.
Thinly slice half of the lemon into rounds and layer them directly on top of the salmon fillet.
Bake for 12 to 15 minutes, depending on the thickness of the fillet, until the salmon flakes easily with a fork and the asparagus is tender-crisp.
Remove from the oven and squeeze the remaining lemon juice over everything before serving immediately.