Using a food processor, chop the nuts 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.
Preheat the oven to 325 degrees . Line 2 cookie sheets with parchment.
On a floured surface, cut the dough into quarters. Pat each dough piece into a 5 1/2-inch round. Transfer the rounds to prepared pans. Bake until the rounds are set in the centers, 18 to 20 minutes.
Transfer the pans to racks; cut each round into 8 wedges while still warm. Sprinkle with the sanding sugar.