Place egg whites in a large bowl; let stand at room temp for 30 minutes. Generously grease and flour a 10 inch tube pan.
In a large bowl, cream butter and sugar until light and fluffy. Add egg yolks, one at a time, beating well after each addition. Beat in lemon peel and extracts. In another bowl, mix flour, baking powder, salt, and cardamom; add to the creamed butter mixture alternately with milk, beating well after each addition.
Beat egg whites on medium speed until soft peaks forms. Fold into batter.
Transfer to prepared pan. Bake at 350 for 50 to 60 minutes or until a toothpick comes out clean. Cool in pan for 10 minutes before removing to a wire rack to cool. Sprinkle with confectioner sugar.
NOTE: for easier removal of cake, use solid shortening when greasing the tube pan.