Preheat your air fryer to 400°F (200°C) for 5 minutes to ensure an even cook.
Pat the salmon fillet dry with a paper towel to ensure the skin and top get a nice sear.
Trim the woody, fibrous ends off the asparagus spears so only the tender parts remain.
In a small ramekin, whisk together the olive oil, sea salt, black pepper, garlic powder, and dried dill.
Brush the herb oil mixture generously over the top and sides of the salmon fillet, then toss the asparagus in the remaining oil.
Place the salmon in the center of the air fryer basket and arrange the asparagus spears in a single layer around it.
Squeeze a small amount of juice from the lemon half over the salmon and asparagus, then place the lemon half cut-side down in the basket to caramelize.
Air fry for 8 to 10 minutes, depending on the thickness of the fillet, until the salmon flakes easily with a fork and the asparagus is vibrant and tender.