Mom'S Tostada Sauce - cooking recipe

Ingredients

1 (16 ounce) can whole tomatoes
8 ounces tomato sauce
1/3 cup finely chopped onion
1/2 teaspoon salt (to taste)
1/4 teaspoon pepper (to taste)
1 teaspoon oregano

Preparation

Combine well in large bowl until tomatoes are in fine bits (I prefer to use my hands).
Refrigerate 3-4 hours to allow flavors to mix.
Pour over tostada and sprinkle with parmesan cheese.