Preheat oven to 350 degrees. Line two large baking sheets with parchment paper.
In the bowl of an electric mixer, beat the butter, ½ c. of the powdered sugar and the vanilla until light and fluffy, about 3 minutes. Gradually add the flour and salt, beating on low speed after each addition until well blended. Mix in the pecans. Shape dough into 1½-inch balls and place on baking sheets.
Bake 15-18 minutes or until bottoms of cookies are lightly browned. Cool 5 minutes on the baking sheets. Roll warm cookies in the remaining ½ c. powdered sugar until evenly coated. Place on wire racks and let cool completely. Store in an air tight container at room temperature.