Position racks in the top and bottom thirds of the oven; preheat to 325 degrees . In a large bowl, using an electric mixer on low, beat the cashews, flour, butter, sugar and vanilla, stopping occasionally to scrape down the sides of the bowl, until well blended.
Using a 1-inch (2 tsp.) cookie scoop, scoop the dough onto two nonstick or parchment-lined baking sheets, spacing about 1 inch apart. Bake until lightly browned, rotating the sheets and reversing from the top to bottom racks halfway through baking, 20 to 25 minutes. Let cool slightly on the sheets.
Place the confectioners' sugar in a large bowl. While the cookies are still warm, roll in the sugar to coat. Transfer to a wire rack and let cool completely.