Preheat your oven to 425°F (220°C).
Pulse the cauliflower in a food processor until it resembles rice. Microwave the riced cauliflower for 5 minutes, then wrap in a clean towel and squeeze out excess moisture.
Mix the cauliflower with a pinch of salt, pepper, and garlic powder to form a thin, even layer on a lined baking sheet. Bake for 15-20 minutes or until slightly golden and crispy.
While the crust bakes, season the chicken breast with salt, pepper, and garlic powder, then grill or pan-sear until cooked through, about 4-5 minutes per side. Once done, dice into bite-sized pieces.
Chop the bell pepper and red onion. Toss them with olive oil, salt, and pepper and roast on a separate tray in the oven for 10-12 minutes beginning in the last part of the cauliflower’s baking time.
Remove the crispy cauliflower crust from the oven and spread a thin layer of tomato sauce on top. Layer the diced chicken, roasted bell pepper, red onion, and fresh spinach evenly.
Sprinkle the part-skim mozzarella cheese on top and return the pizza to the oven for an additional 5 minutes, just until the cheese melts.
Slice and serve warm, enjoying the blend of crispy, tender, and fresh flavors in every bite.