* Do not put the egg yolks together as they will be used individually.
Peel apples, cut in half and core. Cut decorative lengthwise slits in apples, about 1/2-inch deep. Sprinkle with lemon juice and sugar. Set aside. Cream butter and sugar together. One at a time, beat in egg yolks. Gradually beat in lemon juice and grated peel. Sift baking powder and flour together. Gradually add to batter. Blend in milk and rum. In a small bowl, beat egg whites until stiff. Fold into batter. Generously grease a spring form pan. Pour in batter and top with apple halves. Brush apples with oil. Bake in a preheated 350 degree F. oven for 35 to 40 minutes. Remove from pan and sprinkle with confectioners' sugar.