Preheat the oven to 400 degrees F. Line a baking sheet with parchment paper. Break the cauliflower into florets and pulse in a food processor until fine. Line a steamer basket with a kitchen towel (not terrycloth); set in a saucepan with 2 inches simmering water. Add the cauliflower, cover and cook 5 minutes. Drain well, then wring dry in the towel to get out all the moisture. Let cool.
In a bowl, combine the cauliflower with 1/2 cup mozzarella, the parmesan, oregano, 1/2 teaspoon salt, the garlic powder and eggs. Transfer to the center of the baking sheet and spread into a 10-inch circle to make a pizza crust. Bake until golden, about 20 minutes.
Spread the marinara sauce on the crust; top with bell peppers and onion and sprinkle with the remaining 1/2 cup mozzarella. Return to the oven and bake an additional 10 minutes.
Photograph by Con Poulos
Recipe courtesy of Katie Lee for Food Network Magazine