Preheat oven to 375. Prepare a jelly roll pan with cooking spray. Prepare dough according to package directions and then press into pan, forming the crust with one-inch edges. Prick the crust with a fork several times.Bake for ten minutes. In a skillet, cook chicken and onions until chicken is no longer pink. Stir in tomato sauce, pizza seasoning, oregano, and salt. Mix well and heat through. Spoon mixture evenly onto baked crust. Sprinkle spinach and cheeses evenly over the top. Bake for 25 minutes, or until the crust is lightly browned.