Wash and pick over cranberries. Drain and combine with sugar in the bowl of a food processor or blender. Puree as finely as possible.
Press the puree through a medium-fine strainer to remove the toughest skins. You will end up with about 1/3 cup tough dry pulp and skins to discard. Stir strained raspberry preserves into puree. Sauce may be prepared and refrigerated for at least 3 weeks, or frozen for 6 months or longer. Never heat sauce, even to thaw.
To serve, spoon onto plate next to dessert.
From the Dinner Co-op