Preheat oven to 350 degrees. In small saucepan combine tomato sauce, oregano, garlic and onion powders. Bring to a boil. Reduce heat and simmer, covered, for 5 minutes.
Cut pitas in halves, making 8 rounds. Arrange in a single layer on a cookie sheet. Bake until crisp, 3-5 minutes. Remove from oven.
Spoon hot tomato sauce over each pita. Sprinkle with mozzarella cheese, then parmesan cheese. Bake until cheese melts, 5-7 minutes.