If you heat pasta sauce from a jar, it is important to follow the manufacturer's instructions carefully. Some manufacturers recommend heating the sauce on the stove before serving, while others suggest microwaving it for a short amount of time. Either way, make sure to stir the sauce constantly to prevent it from sticking to the bottom of the pan or burning. If you do not heat the sauce, use it as is, but beware that it may be more tart and acidic than if it had been cooked on the stove.