I like this sauce for ravioli because it is thick and adheres to the pasta.

Ingredients

1/4 cup olive oil
1 cup onion, diced
3 tablespoons (about 6-8 cloves) garlic, peeled and minced
2 28-ounce cans of whole Italian tomatoes
1-14 oz container of finely diced or crushed Italian tomatoes
2 teaspoons dried oregano
teaspoon chili flavored tomato paste
1 1/2 teaspoons salt
1/4 teaspoon ground black pepper
20 basil leaves, chiffonade
Ravioli
Parmesan cheese

Directions

Pour the oil into a large pot over medium heat.
Stir in the onion and continue cooking, stirring often, until the onion is soft. This takes about 5 minutes.
Add the garlic and cook, stirring often, for another 1 minute.
Pour in the cans and use a wooden spoon to break the tomatoes into pieces.
Add the remaining ingredients. Cover and bring to a boil, stirring occasionally.
Turn the heat down to keep it at a simmer. Simmer, uncovered, for about 11/2 hours.

Cook ravioli according to package instructions.
Tip: to drain the ravioli, set a colander in a large serving bowl. Gently scoop the cooked ravioli out of the water with a spider. Set the colander aside and drain the water from the serving bowl The bowl is now warm. Add a layer of ravioli, spread a layer of sauce, and sprinkle with Parmesan cheese. Serve immediately.