Start by preheating your oven to 400°F (200°C). Remove the leaves and stem from the head of cauliflower, then cut it into florets. Place the florets in a food processor and pulse until they resemble rice or fine crumbs.
Transfer the cauliflower rice to a microwave-safe bowl and add the 3 tablespoons of water. Cover the bowl with a microwave-safe lid or plastic wrap, and microwave for about 5-7 minutes until softened. Once cooked, let it cool slightly.
To achieve that perfect crust texture, it's crucial to remove excess moisture. Place the cooked cauliflower in a clean kitchen towel or cheesecloth and wring it out to extract as much water as possible.
In a mixing bowl, combine the drained cauliflower, egg whites, mozzarella cheese, garlic powder, oregano, basil, onion powder, and smoked paprika. Stir until everything is well incorporated.
Line a baking sheet with parchment paper. Transfer the cauliflower mixture onto the sheet, and using your hands or a spatula, shape it into a round pizza crust, about 1/4 inch thick.
Bake the crust in the preheated oven for about 25-30 minutes, or until it turns golden brown and crispy.
Once the crust is baked, remove it from the oven and spread the pizza sauce over the top. Sprinkle the diced green peppers, mushrooms, red onion, and black olives evenly across the sauce. Top with a bit more mozzarella cheese if desired.
Return the pizza to the oven and bake for an additional 10-15 minutes, or until the cheese is bubbly and melted.