Preheat oven to 425°.
Boil water for pasta. Cook ravioli until they rise to the top. If
you are making spaghetti cook two minutes less than the
package. Drain pasta.
Heat oil in a large saucepan over medium heat. Add onion and
garlic, and season with salt and pepper. After about five
minutes, onions will be translucent. Add oregano and tomatoes.
Bring to a boil, reduce heat, and simmer, breaking up tomatoes
with spoon, about 30 minutes.
Combine pasta and sauce and pour into a 9 x13 baking dish.
Sprinkle cheese over top and bake 20-25 minutes.