This light, refreshing, low-sugar dessert is perfect for everyday or entertaining. Best of all, it has only four ingredients and 25 calories! Start by making the simple syrup. Add water to a sauce pan and sugar substitute. Then add orange rind strips to flavor the syrup. Reduce heat and simmer. Strain the orange rind pieces. Allow the syrup to cool completely. Stir in fresh grapefruit juice. Next stir in fresh lemon juice. Transfer the mixture to a baking pan and then freeze. Break the mixture in to pieces and transfer to a food processor until it is smooth but not thawed. This makes a pretty holiday dessert.