I adore cranberries—here at Witch Central (North), they're a wintertime staple—but most standard cranberry preparations involve truly toxic amounts of refined sugar. Fruit-sweetening seems a smart (to say nothing of aesthetically-preferable) alternative.
To palates accustomed to commercial cranberry sauces, the fruit-sweetened variety can at first seem overwhelmingly tart. (Unsurprisingly, witches value tartness, both behavioral and gustatory.) If you find that this is true for you, just up the proportion of grapes to cranberries.
Old Warlock's Fruit-Sweetened Cran-Grape Sauce
12 oz. (1 bag) fresh cranberries
1 generous bunch table grapes (red, white, or purple)
apple cider
pinch salt
Pick over the cranberries and wash them. Wash the grapes and stem them.
In a large, non-reactive pot, or slow-cooker, stew the fruit with just enough apple cider to cover the bottom of the pot, and a pinch of salt. (A little salt always brings out the sweetness, my grandmother used to say.) Cook until the fruit falls apart. You may need to help the grapes out a little with a potato masher.
Run the resulting puree through a food mill, or push it through a sieve, to catch the skins. Stir well or whisk to homogenize the texture; then refrigerate. The sauce will thicken as it chills.
Serve and enjoy. Happy eating to you and yours, from one witch to another.