Spread butter evenly in an ungreased 13-in. x 9-in. baking pan. In a large bowl, beat eggs, brown sugar and vanilla until blended. Combine flour, baking soda and salt; gradually add to egg mixture until well blended. Stir in pecans.
Spread into prepared pan. Bake at 350° for 30-35 minutes or until browned. Dust with confectioners' sugar. Cool on a wire rack. Cut into bars.