From http://www.greatpartyrecipes.com/pizza_sauce_recipes.html:

Tomato Herb Sauce (Marinara Sauce)

2 tablespoons extra-virgin olive oil
1 tablespoon minced fresh garlic
1/4 cup finely chopped onion
1 cup tomato sauce
1 teaspoon dried oregano
1 teaspoon dried basil
1/2 teaspoon salt
1/4 teaspoon black pepper
2 tablespoons tomato paste

In a medium saucepan, sauté garlic and onions in olive oil until tender. Add seasonings and continue cooking a few more minutes. Stir in tomato sauce, and then tomato paste. Simmer on low heat for about 10 minutes. Makes about 1 1/2 cups.