1. Wash and, if desired, peel the fruit, then slice it and place in a bowl.
2. Sprinkle the superfine sugar and the salt over the fruit and stir gently. Cover and set aside at room temperature or in the refrigerator, stirring every half hour or so.
3. When you are ready to assemble the dessert, add the liqueur if you are using it.
4. You can prepare the fruit early in the day for a dinner dessert.