2 1/2 cups white sugar
1 teaspoon cornstarch
3/4 cup milk
1/4 cup butter
2 eggs
3/4 cup milk
1 teaspoon vanilla extract
4 cups all-purpose flour
1/2 teaspoon salt
3/4 cup milk
1 tablespoon cornstarch
3/4 cup confectioners' sugar
1/2 teaspoon lemon zest
3 tablespoons water
Lightly grease and flour a 9-inch square pan. Sift together the flour and salt. Set aside. In a medium saucepan combine the milk, butter, and eggs; whisk until smooth. Add the vanilla and flour mixture; stir until all ingredients are thoroughly combined.
In a large bowl, stir together the milk mixture, eggs and 1/2 cup of milk; pour into prepared pan. Spread evenly over cake. Let cool completely in pan before icing.
To make the frosting : Combine confectioners' sugar, lemon zest and 2 tablespoons water in a medium saucepan. Cook over medium low heat, stirring constantly, until smooth. Stir in 3 tablespoons butter or margarine to the mixture. Pour over cake and let cool until cake can be handled, approximately 8 to 10 more minutes.