Sift together flour, baking powder and salt. Beat egg yolks until thick. Beat in half cup sugar and add half cup thawed lemonade concentrate, alternating with flour mix. Beat egg whites and remaining sugar until stiff peaks form. Fold into lemon mix. Spread in greased and floured jelly roll pan and bake at 375 15 to 20 minutes. Immediately loosen sides and invert onto towel sprinkled generously with powdered sugar. Roll up carefully. Let cool on rack. Prepare vanilla whip dessert mix according to directions, substituting quarter cup lemonade concentrate instead of water. Unroll cake, spread filling and re-roll. ----