Prep the broccoli: Rinse and dry the florets well. Moisture prevents crisping, so pat thoroughly with a towel.
Season: In a large bowl, toss broccoli with oil, garlic powder, onion powder, salt, pepper, and paprika if using.
Coat evenly without drenching.
Preheat the air fryer: Set to 390–400°F (200°C). A hot basket helps the broccoli sear and caramelize quickly.
Air fry the broccoli: Arrange in a single layer if possible. Cook for 6–8 minutes, shaking halfway, until the edges are lightly browned and the stems are just tender.
Add cheese: Sprinkle shredded cheese (and Parmesan if using) over the broccoli.
Return to the air fryer for 1–2 minutes, just until the cheese melts and bubbles.
Finish and serve: Squeeze a little lemon over the top if you like and add red pepper flakes. Taste and adjust salt and pepper. Serve hot.