Preheat the oven to 400 degrees F (204 degrees C). Place a piece of parchment paper onto a pizza peel if you plan to use a pizza stone (recommended), or a pizza pan.
Pulse the cauliflower florets in a food processor until they are the consistency of rice. (Use the grate attachment if you have one.)
In a saute pan on the stove, stir fry the cauliflower for about 10 minutes, until the cauliflower is very soft. (This is important! The texture will be off if it's still crisp, so keep cooking until nice and soft.)
Meanwhile, in a large bowl, whisk the egg. Stir in the mozzarella cheese. If using Italian seasoning and garlic powder, stir those in as well.
When the cauliflower rice is cooked through and soft...Option 1 (more effort - recommended if making one large pizza): Place the cauliflower rice into a kitchen towel and squeeze over the sink.Option 2 (easier - better for making 2 smaller pizzas): Stir the cauliflower rice directly into the egg/cheese mixture.With both options, make sure it's mixed very well. You may need to press with a spatula.
Spread the "dough" onto the parchment paper with your hands, to about 1/4" thick. You can make one large pizza or two smaller pizzas, depending on which option you chose in the previous step.
If using a pizza stone (recommended for best results), use the pizza peel to transfer the parchment paper onto the stone in the oven. Otherwise, just place the pan into the oven. Bake for about 20 minutes, until the top is dry and firm, and the edges are a little golden.
Let the pizza crust cool for at least 5-10 minutes at room temperature to firm up more. Add desired toppings. Return to the oven for about 5-10 minutes, until cheese melts.