Preheat air fryer to 375°F.
In a large bowl, whisk together flour, water, garlic powder, salt, and pepper until smooth.
Dip cauliflower florets into the batter, shaking off excess, and place in a single layer in the air fryer basket sprayed with cooking spray.
Air fry for 12 minutes, shaking the basket halfway through, until golden and crispy.
In a separate bowl, mix buffalo sauce and melted butter, then toss the cooked cauliflower in the sauce.
Return sauced cauliflower to air fryer for 3 more minutes to set the coating.
Serve immediately with ranch or blue cheese dressing.