Preheat air fryer to 400°F. Trim woody ends from the ASPARAGUS, rinse, and pat it dry.
Spray or toss ASPARAGUS with OIL until lightly coated.
Arrange in a single layer in the air fryer basket. They can touch, just don't stack.
Air fry 5–7 minutes for medium stalks, until tender-crisp. Adjust time for thinner or thicker spears. Shake the basket halfway through if needed for even browning, and check early to avoid overcooking.
Season with SALT, PEPPER, and optional PARMESAN. Serve.
Refrigerate in an airtight container up to 5 days.
Notes
Oil for crisping - Oil helps the asparagus brown and keeps it from drying out.Asparagus size - Thicker spears take longer. Try to cook similar-sized items together for more even results.Batch size - A ½ pound of asparagus fits in a 5.8 quart air fryer basket without overlap.Add cheese when serving - Sprinkle Parmesan over the asparagus after cooking for easier cleanup.Finish with acid - A squeeze of lemon at the end brightens the flavor.