Preheat oven to 425 degree F. Lightly coat a 12-inch cast-iron or heavy oven-going skillet with nonstick cooking spray. Unroll 1 package of pizza dough; gently pull into a circle. Place dough in prepared skillet; press dough into bottom and halfway up sides of skillet. Bake 5 minutes; remove from oven. Dough will have puffed slightly.
Meanwhile, in large skillet cook onion and garlic in 2 tablespoons of the oil about 5 minutes or until tender. Add spinach, 1/4 teaspoon salt, and 1/4 teaspoon ground black pepper. Cook and stir 1 minute more. Remove from heat; set aside. In a small bowl combine ricotta cheese, 1/4 cup of the pizza cheese, parsley, 1/4 teaspoon salt, and the crushed red pepper. Spoon spinach mixture evenly over bottom of partially baked crust.
Spread ricotta mixture over spinach layer. Top with tomatoes; drizzle with 1 tablespoon of the oil. Sprinkle with 3/4 cup of the remaining pizza cheese. Unroll remaining pizza dough; shape into a 12- to 13-inch circle. Lay dough round on layers in skillet. Brush with remaining oil. Bake 15 to 20 minutes or until top is golden. Top with remaining pizza cheese. Bake 2 to 3 minutes or until cheese is melted. Let stand 10 minutes. Makes 8 servings.