In a 10-inch skillet, combine all of the ingredients and bring to a simmer over medium-high heat. Then, reduce to maintain a gentle simmer. Cook, stirring occasionally, until the liquid has thickened somewhat and looks slightly syrupy, about 30 minutes.
Remove the cinnamon stick and let the cranberry sauce cool in the pan. It will thicken a bit more as it cools. Serve slightly chilled or at room temperature.
Notes
If preparing this recipe as gluten-free, just be sure to use a brand of maple syrup that is known to be GF.
12 tangerines is an estimate (depends on the size of your tangerines and how juicy they are). You can also buy fresh squeezed tangerine juice and strain out the pulp. I use half tangerine juice and half orange juice and it turns out wonderful. You do need the zest from a tangerine, so be sure to use at least one fresh one.
Be sure to remove the cinnamon stick when the sauce is done simmering. The cinnamon flavor will be plenty noticeable, but you don't want it to overpower.
This sauce may be made up to a week ahead. Just cover and chill.