Preheat the oven to 430℉ while mixing the seasonings: In a large bowl, whisk together 1/2 tsp garlic powder, 4 fl oz water, 1 tsp paprika, 3 tbsp cornstarch, 1/2 tsp onion powder, 1/2 cup all-purpose flour, and 1 tbsp unsalted butter.
Add 20 oz cauliflower to the bowl and toss well to combine.
Place the cauliflower in a single layer on the baking sheet. Bake for 15 minutes.
While waiting, mix the bang bang sauce: In a small bowl, mix 1 tbsp of cornstarch, 1/4 tsp red pepper flakes, 2 tbsp Heinz ketchup, 2 tsp brown sugar, 1 tbsp reduced-sodium soy sauce, 1 tbsp rice vinegar, 2 fl oz pineapple juice, 2 fl oz water, and 1 tsp sriracha.
Heat 1 tbsp olive oil in a skillet over medium heat. Add 1 tsp garlic and 1 tsp ginger and sauté until fragrant.
Add the bang bang sauce to the skillet. Stir constantly for 1 minute until it thickens, then turn off the heat.
Add the baked cauliflower florets to the skillet and toss them with the bang bang sauce.
Remove from the stovetop. Garnish with 2 tbsp scallions, 1/4 tsp ground black pepper, 1/2 tbsp sesame seeds, and 1/4 tsp red pepper flakes. Serve hot.