Stir in the cranberries, orange zest and cinnamon stick, if using, and salt. Bring the mixture back to a simmer. Cook, stirring and mashing the berries occasionally, until the sauce has thickened. Note that it will thicken more as it cools.
12 oz. cranberries, 2 strips orange zest, 1 (3-inch) cinnamon stick, ⅛ tsp kosher salt