In a small bowl, cream butter and sugar until light and fluffy, 5-7 minutes. Beat in vanilla. Add the flour, beating on low speed just until combined. Stir in pecans. Cover and refrigerate for 30 minutes or until easy to handle., Shape 1/2 cups into 1/2-in.-thick logs. Cut logs into 2-in. pieces. Place 2 in. apart on greased baking sheets. Bake at 350° for 15-18 minutes or until lightly browned. Roll warm cookies in confectioners' sugar; cool on wire racks.