LUSCIOUS LEMON LAYER CAKE

Steps:

• Prepare cake mix according to package directions, using a greased 9-in. square baking pan. , Bake at 350° for 18-20 minutes or until a toothpick inserted in the center comes out clean. Cool for 10 minutes before removing from pan to a wire rack to cool completely., For filling, combine the sugar, cornstarch and salt in a saucepan. Gradually stir in water until smooth. Bring to a boil; cook and stir for 2 minutes or until thickened. Remove from heat; stir in butter, lemon zest and food coloring if desired. Gradually stir in lemon juice. Cool completely. , For frosting, in a small bowl, beat butter until fluffy. Gradually add the confectioners' sugar, lemon juice, lemon zest and enough milk to achieve desired spreading consistency. , To assemble, cut cake in half lengthwise. Trim outside edges. Place one half on a serving platter. Top with the lemon filling. Top with remaining cake; spread with frosting.