Make a cranberry orange syrup:
Put the cranberries, orange juice, orange zest and sugar in a large saucepan.
Cook over medium heat until the cranberries break down and the liquid is slightly thickened to a syrup stage which should take about 10 to 15 minutes.
Put the mixture into a blender and blend well.
Caution: Hot liquids in a blender can be dangerous. Be sure to cover the top of the blender with a towel. Make a vent in the blender lid by loosening the center cap. Start slow then speed it up slowly.
Strain and discard any solids and set aside to cool.