Preheat oven to 400°F (200°C). Line a baking sheet with parchment paper.
Rice the cauliflower using a food processor until it resembles fine crumbs.
Spread cauliflower on the baking sheet and roast for 15 minutes. Let it cool.
Transfer cooled cauliflower to a nut milk bag or clean towel and wring out as much water as possible.
In a large bowl, mix the cauliflower with egg, parmesan, mozzarella, garlic powder, Italian seasoning, and salt.
Line a new baking sheet with parchment paper. Press the cauliflower dough into a thin, even 10–12" circle (¼ inch thick).
Bake at 425°F (220°C) for 20–25 minutes, or until golden and crisp around the edges.
Add desired toppings, then return to the oven for 10 minutes or broil until bubbly and golden.