Combine spinach and ricotta cheese in a small bowl; in a separate bowl, combine the pinto and black beans. Cut 3 tortillas into pieces and arrange them in a solid layer to cover the bottom of an 8" square baking dish coated with cooking spray; top with half each of beans, salsa, spinach mixture and cheese and then repeat layers with remaining ingredients. Cover and bake at 425° for 25 minutes; uncovered and bake an additional 15 minutes. Let stand 10 minutes before serving.
