How to Make It
Heat oven to 350° F. Spread the walnuts on a rimmed baking sheet and toast in oven, tossing occasionally, until fragrant, 6 to 8 minutes; let cool. In a food processor, process the walnuts until finely ground.
In a large bowl, whisk together the ground walnuts, flour, cinnamon, and salt; set aside.
Using an electric mixer, beat the butter and ⅓ cup of the sugar on medium-high until light and fluffy, 2 to 3 minutes. Beat in the vanilla.
Reduce mixer speed to low and gradually add the flour mixture, mixing until just combined (do not overmix).
Shape the dough into balls (about 1 tablespoon each) and place 2 inches apart on baking sheets.
Bake, rotating the baking sheets halfway through, until just beginning to brown, 12 to 14 minutes. Let cool slightly on the baking sheets, then transfer to a wire rack to cool completely.
Place the remaining ⅓ cup of sugar on a plate. A few at a time, roll the cookies in the sugar to coat, then dust with additional cinnamon.