Move oven rack in the lowest position; preheat to 450°F. Coat a large baking sheet with cooking spray or sprinkle cooking stone with flower.

Roll out dough on a lightly floured surface to about the size of the baking sheet. Transfer to the baking sheet and add marinara sauce. Bake until puffed and lightly crisped on the bottom, 8 to 10 minutes.

Meanwhile, heat oil in a large nonstick skillet over medium heat. Add onion, prosciutto and crushed red pepper, stir until the onion is beginning to brown, about 3 minutes.

Spread the onion mixture evenly over the crust and top with cheese. Bake until crispy and golden and the cheese is melted, 8 to 10 minutes. Remove from the oven and top with arugula and tomato. Cut and serve.