Preheat the air fryer: Set it to 390°F (200°C). A hot basket helps get those crispy edges fast.

Prep the broccoli: Rinse and dry the florets well. Excess moisture will steam the broccoli and prevent crisping.

Season: In a large bowl, toss the broccoli with olive oil, salt, pepper, garlic powder, and red pepper flakes if using. Make sure every floret is lightly coated.

Add parmesan and zest: Sprinkle in the grated parmesan and lemon zest. Toss again so the cheese clings to the oiled florets.

Arrange in the basket: Spread broccoli in a single layer. A little overlap is okay, but avoid a thick pile. Work in batches if needed.

Air fry: Cook for 7 to 10 minutes, shaking the basket once halfway through. Broccoli is done when the edges are browned and the stems are crisp-tender.

Finish: Transfer to a bowl. Drizzle with melted butter and a squeeze of lemon juice if you like. Taste and adjust salt and pepper. Add a final dusting of parmesan.

Serve hot: Enjoy right away while the cheese crust is still crisp.