Sift together flour, salt, and baking powder.
Cream butter and granulated sugar. Add egg yolks, one at a time. Beat for one minute.
Add lemon juice alternately with dry ingredients, beginning and ending with dry and blending thoroughly after each addition. Add lemon rind and ½ cup pecans.
Beat the egg whites until soft mounds begin to form. Add in confectioner's sugar slowly, beating well after each addition. Continue beating until egg whites are stiff - straight peaks are formed when the beater is raised.
Gently but thoroughly fold egg whites into lemon batter. Pour into well-greased and lightly floured 13x9 inch pan.
Bake at 400 degrees for 20-27 minutes. While still warm, frost. Sprinkle with remaining pecans.
Cream butter and blend in confectioner's sugar alternately with cream. Beat until creamy.