Spaghetti with Olives and Tomato Sauce

• 1 pound dried spaghetti
• 1/4 cup olive oil
• 1 1/4 cups mixed olives, pitted and halved
• 1/2 tablespoon red pepper flakes, plus more if desired
• 3 cups tomato sauce, recipe follows
• 1/2 cup grated Parmesan
• 1/2 cup basil leaves, shredded

Simple Tomato Sauce:

• 1/2 cup extra-virgin olive oil
• 1 small onion, chopped
• 2 cloves garlic, chopped
• 1 stalk celery, chopped
• 1 carrot, chopped
• Sea salt and freshly ground black pepper
• 2 (32-ounce) cans crushed tomatoes
• 2 dried bay leaves
• 4 tablespoons unsalted butter, optional