A great sauce can take a dish from good to fantastic. In this episode, Martha goes over some classics, starting with béarnaise sauce, a derivative of hollandaise. Next she makes Kansas City barbecue sauce, which is tomato-based with a sweet-tart flavor. Tartar sauce — Martha’s version includes capers, shallots and cornichons — and a tasty cocktail sauce are both beloved staples. Then Martha shows how to make salsa verde, a perfect accompaniment to grilled meats, poultry, seafood and vegetables.