Using a food processor, chop the nuts and cranberries with 2 tbsp. confectioners sugar for 20 seconds. Scrape down and repeat until finely ground. Add the flour and pulse to mix.
Using an electric mixer, combine the butter, remaining 6 tbsp. confectioners sugar, the vanilla and salt; mix at low speed until just blended. Add the nut flour and mix just until incorporated.
Turn out the dough onto a work surface; roll into a 10-inch-long cylinder (about 2 inches in diameter). Roll the log in sanding sugar; wrap in plastic wrap, twisting the ends to seal. Transfer to a baking sheet and refrigerate until firm, at least 1 hour.
Position racks in the upper and lower thirds of the oven; preheat to 325 degrees . Line 2 cookie sheets with parchment.
Using a thin, sharp knife, trim the ends of the dough, then cut crosswise into 24 slices about 1/3 inch thick; transfer to the prepared pans. Bake until lightly golden, rotating and switching the pans halfway through baking, about 18 minutes.
Transfer the pans to racks; sprinkle the hot cookies with more sanding sugar. Let cool on the pan for 3 minutes, then transfer to racks to cool completely