The name of these buttery cookies comes from the word "polvo," which means dust in Spanish, and refers to their cinnamon-sugar coating, as well as the cookie's crumbly texture.
In a medium bowl, whisk together flour, salt, and 1 1/2 teaspoons cinnamon.
In the bowl of an electric mixer fitted with the paddle attachment, beat together butter and 1 cup confectioners' sugar on medium speed until smooth. Beat in vanilla. Reduce speed to low and gradually mix in flour mixture until incorporated. Shape dough into a square and wrap in plastic; refrigerate 1 hour.
On a lightly floured surface, roll out dough 1/2 inch thick. Using a 2 1/2-inch round cutter, cut out cookies. (Scraps can be rerolled once.) Divide evenly between two parchment-lined baking sheets. Using a 3/4-inch round cutter, cut out a hole in the center of each cookie. Refrigerate until firm, about 30 minutes.
Meanwhile, preheat oven to 350 degrees. Bake, rotating halfway through, until edges begin to brown, about 20 minutes. Let cool on sheets 5 minutes, then transfer to a wire rack and let cool completely.
In a small bowl, stir together remaining 2 teaspoons cinnamon and 1 cup confectioners' sugar. Working with one cookie at a time, toss in cinnamon sugar until thoroughly coated. Cookies can be stored in an airtight container at room temperature up to 3 days.