Preheat your oven to 400°F and line a large sheet pan with parchment paper for easy cleanup.
Wash the asparagus and snap off the woody ends, then place the spears on one side of the prepared sheet pan.
Pat the salmon fillet dry with a paper towel and place it on the other side of the pan.
In a small bowl, whisk together the olive oil, lemon juice, minced garlic, sea salt, black pepper, dill, and oregano.
Drizzle the herb mixture over both the salmon and the asparagus, using your hands or a brush to ensure the asparagus is evenly coated.
Slice the half lemon into thin rounds and layer them across the top of the salmon fillet.
Roast in the oven for 12 to 15 minutes, or until the salmon is opaque and flakes easily with a fork and the asparagus is tender-crisp.
Serve immediately while hot, drizzling any extra pan juices over the salmon.