Preheat oven to 450°F. Spray a large baking sheet or pizza pan with nonstick cooking spray.
Cut the florets from the cauliflower and place in the bowl of a food processor. Process for 30 seconds, or until the cauliflower looks like tiny crumbs. Alternatively, grate the whole head of cauliflower using the large holes of a box grater. Place crumbled cauliflower in a large microwave-safe bowl. Microwave for 8 minutes. Let cool.
Place the cauliflower in a kitchen towel and squeeze out as much liquid as possible. Add egg, mozzarella, garlic, salt, pepper flakes, oregano, garlic powder, and olive oil to the cauliflower, stirring to combine. Pat the mixture into about a 12-inch round on prepared pan. Brush with olive oil.
Bake for 12 to 15 minutes, or until golden.
Remove crust from oven and adjust oven setting to broil. Top the pizza with sauce, mozzarella, pepperoni, and any other desired toppings. Broil for 3 to 4 minutes, watching carefully, until the cheese is melted, bubbling, and begins to brown. Cut into slices and serve hot.