In this well-known Sicilian dish, eggplant, bell peppers, celery and onions are cooked separately so that they retain their individual character, then these ingredients are simmered together with tomatoes in a sweet-and-sour sauce. Caponata tastes best the day after it is made, once the flavors have had a chance to blend and mellow. It keeps well in the refrigerator but should be brought to room temperature before serving. Accompany it with crusty sesame seed?topped Sicilian bread for soaking up the fragrant sauce. Caponata can be served hot or cold, as an antipasto or a side dish.