Position a rack in the lower third of the oven, place an inverted baking sheet on top and preheat to 500 degrees . Meanwhile, in a medium skillet, heat 1 tsp. EVOO over medium-high heat. Add the bell pepper and cook until crisp-tender, about 2 minutes. Add the onion, season with salt and pepper and transfer to a plate.
In a large bowl, toss the cauliflower with 2 tbsp. EVOO, the crushed pepper and cumin until coated.
Stretch the pizza dough to fit a second baking sheet lined with parchment. In a bowl, combine the garlic and remaining 2 tbsp EVOO. Brush the garlic oil onto the dough; layer with the cheese, onion mixture and cauliflower; season with salt.
Place the baking sheet on top of the one in the oven and bake, rotating halfway through, until the crust is golden, about 20 minutes.