Ingredients

  • 1 package (9 ounces) yellow cake mix
  • 3 tablespoons sugar
  • 1 tablespoon cornstarch
  • Pinch salt
  • 3 tablespoons water
  • 3/4 teaspoon butter, softened
  • 1/4 teaspoon grated lemon zest
  • 1 drop yellow food coloring, optional
  • 4-1/2 teaspoons lemon juice
  • 3 tablespoons butter, softened
  • 1-1/2 cups confectioners' sugar
  • 1 teaspoon lemon juice
  • 1 teaspoon finely grated lemon zest
  • 1 to 2 tablespoons whole milk

Method

  • 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.