Into a medium saucepan over medium heat, combine the sugar, orange juice, and liqueur. Stir frequently until sugar is dissolved.
Add the cranberries. Cook and stir frequently 10 minutes, or until the cranberries begin to pop open.
Remove from heat and allow to cool.
Pour the sauce into a serving bowl and refrigerate at least overnight. Sauce will thicken as it cools.
Serve slightly chilled or room temperature.