Preheat oven to 220 degrees C. Line a muffin tin with baking paper squares.
Grate cauliflower into a microwave-safe bowl using a fine grater. Chop up any remaining pieces that are too small to grate but too big for the crust.
Microwave cauliflower until soft and tender, 4 to 6 minutes. Pour cauliflower into a clean dish towel cool easily handled, 15 to 20 minutes.
Wrap the towel around the cauliflower and squeeze out as much liquid as possible; the drier the cauliflower is, the better it will hold together as a crust once mixed with the other ingredients.
Combine cauliflower, 1 cup mozzarella cheese, Parmesan cheese, egg, salt, pepper, garlic powder and onion powder in a large bowl.
Scoop cauliflower crust mixture into prepared muffin tin, dividing the mixture evenly among the cups. Pat down cauliflower mixture with the back of a spoon, making it compact.
Bake in the preheated oven until golden brown, about 15 minutes.
Spoon a small amount of pizza sauce onto each cauliflower crust. Top with remaining 1 1/2 cups mozzarella cheese, dividing evenly among the crusts.
Bake until golden brown and cheese is melted, about 15 minutes. Let sit in pan for 5 minutes before moving each bite to a cooling rack. Let cool for 10 minutes. Peel paper squares off the crusts and serve on a platter.
If you've got a food processor, cut the cauliflower into smaller chunks and toss it in the bowl and process until fine.