Slice the very edge root ends off of the orange, just until you see the flesh. Leave the rest of the skin ON the orange and slice it into 8 pieces.
Place the fresh cranberries, orange slices and sugar in your food processor and process until smooth (or until no large chunks remain).
Refrigerate until ready to serve (it tastes best after being in the fridge for at least on hour) or for up to 1 week. Serve over turkey, chicken, pork loin etc.
To make-ahead: Cranberry relish can be made ahead and stored in the refrigerator for up to 2 weeks.To freeze: Store cranberry relish in a freezer safe container for 2-3 months. To use, remove it from the freezer and thaw it in the refrigerator.