In a food processor, combine the pecans and ¼ cup sugar, and process until finely ground, about 30 seconds.
Add remaining sugar along with flour, cinnamon, and salt, and pulse until evenly incorporated.
Add butter and vanilla, and process until dough just comes together and you can form the balls. If the dough is too dry, add 1 to 2 tablespoons of water (1 at the time), and process again until you reach a more solid consistency.
Shape dough into ½" thick balls (I use a small cookie dough scoop for sizing purposes) and place on a tray/plate that you can fit in the fridge. Chill cookies for 30 minutes.
While the cookies chill in the fridge, preheat oven to 350°.
Transfer balls to a parchment paper lined baking sheet, spacing them 2" apart.
Bake the cookies, rotating baking sheet front to back halfway through baking, until lightly browned and set, about 14 to 17 minutes.
Let cool for 5 minutes, and then place in bowl of confectioners' sugar; toss to coat evenly in sugar.