Rinse asparagus and trim 1.0 to 1.5 inches from the woody ends; pat dry thoroughly.
In a bowl, toss asparagus with olive oil, kosher salt, garlic powder, and black pepper until evenly coated.
Arrange asparagus in a single layer in the air fryer basket. Cook for 6 to 8 minutes, shaking or rotating halfway, until tips are crisp and stalks are tender.
Transfer to a plate and finish with red pepper flakes, lemon zest, and Parmesan if using. Serve immediately.
Notes
For thicker asparagus, add 1 to 2 minutes of cook time. Aim for bright green stalks with lightly crisped tips. Great with a squeeze of fresh lemon juice.