Rinse the cranberries and pick out any soft or shriveled berries.
In a medium saucepan over medium heat, stir the sugar, orange juice and water until the sugar dissolves, about 2 minutes.
Add the cranberries, salt and cinnamon stick (if using). Bring to a boil, then reduce to a steady simmer.
Simmer for 10 to 12 minutes, stirring now and then, until most of the berries have burst and the sauce is glossy.
Remove from the heat, take out the cinnamon stick and stir in the orange zest.
Cool for 30 minutes, then move to a bowl or jar. Serve warm or chill for about 2 hours until set.
