Preheat oven to 500ºF. Mist both sides of 2 tortillas with cooking spray. Place tortillas on a baking sheet, top with half of tomatoes, pepperoni and cheese; bake on top rack for 3 minutes. Move to bottom rack and bake until tortillas are puffed and browned around edges, about 3 minutes longer. Sprinkle with half of basil.
While first two pizzas are baking, assemble remaining two pizzas on another baking sheet. Bake as directed above, sprinkle with remaining basil, and serve immediately.