Mix flour and butter into a fine crumb and pat down into an 11" X 7" pan. Bake at 350 degrees for 10 minutes. Beat eggs. Mix brown sugar, nuts, baking powder and vanilla and spread onto hot crumb mixture. Bake at 350 degrees for 20 minutes. Mix confectioners' sugar, lemon rind and juice and spread over hot cake. Cool well and cut into squares. Mrs. John Hopkins Iv