2 tablespoons olive oil
1 small onion, chopped (about 1/2 cup)
1 large clove garlic, finely chopped
1 (35-ounce) can plum tomatoes, with juice
1 teaspoon dried basil
1 teaspoon dried oregano
salt, to taste
freshly ground pepper, to taste

Heat the oil in a medium-size saucepan over medium heat. Add the onion and garlic and cook, stirring, for about 5 minutes until softened. Chop the tomatoes coarsely and add them to the pan along with their juices.
Add the basil and oregano. Bring the sauce to a simmer.