Preheat oven to 425°F. Line a baking sheet with foil. Place a cooling rack on top, and coat lightly with cooking spray.
Whisk together flour, protein powder, garlic powder and buttermilk in a large bowl. Add cauliflower, tossing to coat. Shake excess batter from cauliflower, and place florets on rack. Discard any remaining batter.
Bake 20 minutes. Carefully remove cauliflower from baking sheet with tongs, and toss in hot sauce. Return to rack, and bake another 10–12 minutes, or until cauliflower browns on edges.