In a medium saucepan, combine cranberries, orange zest, cinnamon, orange juice, and brown sugar. Add enough water to cover, and bring to a boil over high heat. Immediately reduce heat, and simmer for about 1 hour, or until the sauce has thickened. Taste for sweetness, and adjust with additional sugar if necessary. You can not overcook, so continue cooking until you have a good thick consistency. Let mixture cool, then refrigerate in a covered container.