a slightly modified recipe from epicurious.com

1 quart tomatoes
1 to 2 garlic cloves, minced
2 to 3 tablespoons olive oil
½ onion, chopped
1 sweet pepper, chopped
1 tsp salt, plus 2 to 3 tablespoons
Freshly ground black pepper
5 to 6 quarts water
14 to 16 ounces spaghetti
3 tablespoons chopped fresh basil
1/2 cup grated Parmigiano-Reggiano for topping pasta (optional)

Peel the tomatoes, if desired, by blanching the tomatoes in boiling water, then chop tomatoes coarsely.

Heat one tablespoon olive oil in a large pan. Add onion and cook over medium heat until translucent. Add garlic and sweet pepper, and cook until the garlic barely begins to color.

Add the tomatoes to the pan and cook over moderately high heat for 5 minutes or until the tomatoes look cooked and moist but not all the liquid has evaporated. Add salt and pepper to taste.

For a smooth sauce, blend the cooked tomatoes in a food processor with the remaining extra-virgin olive oil and return the sauce to the skillet. For a chunky sauce, add the remaining oil before serving.

Bring 5 to 6 quarts of water to a rolling boil. Add 2 to 3 tablespoons salt and the spaghetti; cook until it still offers considerable resistance to the tooth, around three quarters of the cooking time.

Drain the pasta, reserving 2 cups of the cooking water. Add the drained al dente pasta, 1/2 cup pasta-cooking water, and the basil to the skillet with the tomato sauce. Cook over high heat, stirring to mix sauce and pasta, until the pasta is cooked. Add more pasta water if the sauce becomes too dry. Serve immediately, topped with Parmigiano if desired