Reserve 1/2 cup cranberries. Place the remaining cranberries, sugar, 2 1/2 tablespoons water, and orange zest in a saucepan over medium-low. Cook 8 to 10 minutes, stirring occasionally.
Increase heat to medium-high; stir in orange liqueur. Cook 8 minutes or until juices begin to thicken. Remove pan from heat; stir in reserved 1/2 cup cranberries, salt, and pepper.