Preheat oven to 400 degrees F (200 degrees C).
Combine tomatoes, onion, olive oil, oregano, basil and parsley in a medium bowl. Place bread on a baking sheet, and top with tomato mixture. Sprinkle with Parmesan.
Bake in preheated oven for 8 to 10 minutes, or until bottom of bread is browned. Allow to cool 5 minutes before serving.
