Peel, core and coarsely dice apples. Heat sugar and water in heavy large saucepan over low heat, swirling pan occasionally, until sugar dissolves.
Add cranberries, apples and lemon peel. Bring to boil. Reduce heat to medium and cook until consistency of thick jam, stirring frequently, about 20 minutes. Stir in cassis to taste. Cool completely before serving.
Note: Can be stored in refrigerator 1 month.