Mix 1 1/2 cups of cake mix, flour, yeast and 2/3 cup warm water (mix yeast and water, then add cake mix, flour and eggs). Beat 2 minutes at medium speed. Pour into a greased 9 x 13-inch cake pan/pie tin. Spoon on pie filling (fruit of your choice). Mix margarine with rest of cake mix. Pour cake and margarine over top of cake and pie filling. Bake for 30 minutes at 375°. Glaze with water and confectioners' sugar. If the cake proves too rich, decrease margarine or butter to 2 teaspoons.