Beat butter and sugar together in a mixing bowl until fluffy. Add egg yolks, lemon juice and rind and beat until well combined. Add flour and milk and beat again. In another bowl beat egg whites until stiff. Fold egg white gently into the milk mixture. Turn batter out into a greased pudding dish or 9 x 9 pan. Set pudding dish in a shallow pan of water, making sure water is not deep enough to boil over into the pudding. Bake in a preheated 350 oven for about 45 minutes or until toothpick inserted comes out clean. Serve plain or with whipped cream. Serves 6-8.
