Cook cranberries in 2 cups water about 10 minutes or until skins break.
Rub berries through sieve to make smooth pulp.
Stir in sugar, juice and peel.
Stir in 2 cups cold water.
Pour into baking dish, 8x8x2 inches.
Freeze until firm, stirring 2 or 3 times to keep smooth.
Let stand at room temperature 10 minutes before serving.