If you want to add depth to your sauce, try adding sprigs of thyme, a few strips of basil, and a fresh bay leaf. Dried herbs and spices work well, too, like red pepper flakes, smoked paprika, and oregano. Another thing to do is add fat to your sauce, like cream or butter. Black olives and capers can also add some lively flavor, as can any kind of meat, like sausage, ground beef, or veal.