Place cranberries, sugar, orange juice and cinnamon stick in a medium saucepan. Bring to a boil then lower heat and simmer for 8 minutes. Stir occasionally.
Stir in orange zest and Grand Marnier and cook over medium heat for another 10 minutes. It is done when you see the mixture begin to thicken or get syrupy.
Remove from heat and discard cinnamon stick. It will continue to gel as it cools.
Chill. When ready to serve, garnish with additional orange zest, orange peel, or slice of orange.
Notes
HOW TO STOREAllow the cranberry sauce to cool to room temperature. Transfer it to a glass airtight container and refrigerate for up to 2 weeks.To Freeze: Place the cooled cranberry sauce in a freezer-safe container and freeze it for up to 4 months. Thaw the sauce in the refrigerator overnight prior to serving.