Preheat air fryer to 400°F (200°C) for 3 minutes.
In a large bowl, toss the cauliflower with olive oil, salt, paprika, garlic powder, pepper, and cayenne.
Air fry at 400°F for 14–18 minutes, shaking halfway, until golden-brown and crisp on the edges.
While it fries, melt butter in a small pan, add garlic, cook 30 seconds, then stir in lemon juice.
When cauliflower is done, toss immediately in garlic butter, then sprinkle with Parmesan and parsley.
Serve right away, or plate with a side of aioli or tahini-lemon dip.