*There is no substitute for sun-ripened, DOP-certified Italian tomatoes. Using the standard tomatoes from grocery stores will result in a sauce that is bland and flavorless. The DOP San Marzano tomatoes are widely considered the best. You can also find them in specialty stores. If you can't find DOP-certified San Marzano's, use another quality Italian-imported brand.
*Either freeze the meatballs raw and make the sauce the day you're ready to eat them or freeze them cooked in the sauce. Place them single-layer in ziplock freezer bags. Thaw completely and slowly reheat them to retain moistness.