Cream shortening in a bowl; gradually add sugar, beating well. Beat egg yolks until thick and lemon colored. Add to creamed mixture, mixing well.
Sift together flour, baking powder, salt, cinnamon, and nutmeg. Add to creamed mixture alternately with milk, beginning and ending with flour mixture; stir just until dry ingredients are moistened.
Beat egg whites (at room temperature) until stiff but not dry. Fold egg whites and berries into batter. Spoon into a greased 9- inch square baking pan. Bake at 375° for 45 minutes or until a wooden pick inserted in center comes out clean. Cut into squares, and serve warm.