Luscious Lemon Squares

2 tablespoons butter
1 cup granulated sugar
3 tablespoons all-purpose flour
Juice and zest of 2 lemons
2 eggs, separated
1 cup milk
Whipped cream, to garnish

Mix butter, sugar, flour, lemon juice, milk, and egg yolks. Beat the egg whites until stiff and add to the mixture. Bake at 350 degrees F for 40 minutes in a buttered, 8-inch square pan set in a pan of water. Serve warm or cold, topped with whipped cream, if desired.