To prepare the tomato sauce, heat the olive oil and butter in a large skillet over medium heat. Add the onion and cook for 2 minutes. Then, add the celery and cook for 5 minutes, or until it turns tender. Add the tomatoes, tomato sauce, garlic, oregano, basil, 1 teaspoon salt, and ¼ teaspoon pepper and cook them over low flame for about 10 minutes.