Position a rack in the middle of the oven and preheat to 325F. Line a baking sheet with parchment paper.
In a bowl, sift together the flour and salt. Set aside.
In the large bowl of an electric mixer fitted with the paddle attachment, combine the butter, sugar, and vanilla. Beat on medium speed until smooth, about 1 minute. Add the hazelnuts, and beat on low speed until blended. Add the dry ingredients and beat until the soft dough comes together in large clumps.
To form each cookie, roll a level tablespoon of dough between your palms into a 1-inch ball. Place the balls 1 inch apart on the prepared baking sheet. Make sure to set them firmly onto the baking sheet so they stay in place.
Bake the cookies until the bottoms are light brown and the tops are lightly colored, 10-25 minutes.
Sift the confectioners’ sugar into a bowl. While the cookies are still slightly warm, gently roll the cookies in the sugar to coat them evenly. You will not use all of the confectioners’ sugar. Store in an airtight container at room temperature for up to 3 days.