In a large bowl, combine the cake mix, gelatin, water, egg whites, applesauce, oil, lemon extract and food coloring if desired; beat on low speed for 30 seconds. Beat on medium for 2 minutes. Pour into a 13 by 9 inch baking pan coated with cooking spray. Bake at 350° for 25-30 minutes or until edges are lightly browned and a toothpick inserted near the center comes out clean. Cool on a wire rack for 10 minutes. Meanwhile, for glaze, in a small bowl, combine confectioners? sugar and lemon juice until smooth. Drizzle about a third of glaze over cake; carefully spread evenly. Repeat with remaining glaze. Cool completely.