Preheat oven to 450°F. Grease a baking sheet with cooking spray or line it with parchment paper.
In a large bowl, whisk together flour, water, garlic powder, paprika, salt, and pepper until a smooth batter forms. Add cauliflower to the batter and toss to coat evenly.
Spread the coated cauliflower onto the prepared baking sheet in a single layer, ensuring space between each piece. Bake in the preheated oven until lightly browned, approximately 20 to 25 minutes, flipping over halfway through.
Meanwhile, in a small bowl, combine hot sauce, melted butter, and lemon juice until well blended.
Brush the buffalo sauce mixture onto the baked cauliflower and return to the oven. Bake for an additional 15 minutes or until the cauliflower begins to brown.
Serve hot with optional sides such as ranch dressing, celery, and carrots.