In the bowl of a stand mixer fitted with the paddle attachment, combine the almond flour, cocoa powder, tapioca starch, sugar, cinnamon, salt, and cayenne. Add the pecans, butter, and vanilla. Mix on low until the butter is incorporated and the dough forms large clumps, 1 to 2 minutes. If you don’t have a stand mixer, use a pastry cutter to blend the butter into the dough. Cover the dough with plastic wrap and refrigerate for 30 minutes.

Meanwhile, position a rack in the center of the oven and preheat to 350ºF. Line a rimmed baking sheet with parchment paper.

Sift the powdered sugar into a shallow bowl. Form about 32 (1-inch) balls of dough (about a tablespoonful each) and roll them in the powdered sugar, knocking off any large clumps. Place the balls on the prepared baking sheet 1 inch apart, then bake until slightly puffed and cracked, 18 to 22 minutes. The cookies will be soft but will crisp up when cool; if they’re still soft when cool, return them to the oven to bake a bit longer. When cool, roll each cookie a second time in the powdered sugar and serve.