Spinach Pierogi Pizza

-into rings Heat oven to 425 degrees. Grease 13 x 9" pan. Unroll dough and place in greased pan; starting at center, press out with hands. Bake for 7 to 9 minutes or until light golden brown. Meanwhile, in large skillet cook spinach and chopped onion in butter until onion is crisp-tender. Stir in potatoes; mix well. In small bowl, combine oil and garlic salt; mix well. Brush over partially baked crust; top with spinach mixture. Sprinkle with mozzarella and then Cheddar cheeses; top with onion rings. Bake for another 15 to 20 minutes or until cheese is melted and edges of crust are golden brown.