Preheat oven to 450°F. Grease a baking sheet with cooking spray or line it with parchment paper.
In a large bowl, whisk flour, water, garlic powder, paprika, salt and pepper until batter is smooth. Add cauliflower to batter and toss to coat.
Spread cauliflower onto the prepared baking sheet in a single layer with space between them. Bake in the preheated oven until lightly browned, about 20 to 25 minutes, flipping over halfway through.
In another small bowl, combine the hot sauce, melted butter and lemon juice until well blended. Brush the buffalo sauce mixture on the cauliflower.
Return to the oven and bake until they start to brown, about 15 minutes.
Serve hot with ranch dressing, celery and carrots, if desired