01 - Rinse cranberries thoroughly and discard any that are soft or bruised.
02 - In a medium saucepan, mix cranberries, orange zest, orange juice, sugar, water, and cinnamon if using.
03 - Heat mixture over medium-high heat until it reaches a boil, stirring occasionally.
04 - Reduce heat to medium-low and simmer for 10 to 12 minutes until cranberries burst and sauce thickens, stirring occasionally.
05 - Remove from heat and let sauce cool to room temperature to allow further thickening.
06 - Transfer sauce to a serving dish or airtight container and refrigerate until ready to serve.