Step 1: In a medium saucepan, combine the sugar, water, and orange juice over medium heat.
Step 2: Stir occasionally until the sugar has completely dissolved and the mixture reaches a gentle boil.
Step 3: Add the fresh cranberries, orange zest, cinnamon stick, and a pinch of salt to the saucepan.
Step 4: Bring the mixture back to a simmer. Cook for about 10 minutes, or until the cranberries have popped and the sauce has begun to thicken slightly.
Step 5: Remove the saucepan from the heat and discard the cinnamon stick. Let the sauce cool to room temperature before transferring to a container.
Step 6: Refrigerate for at least 2 hours (or overnight) to allow the sauce to fully set and the flavors to meld.