Cream the sugar, butter and lemon rind until fluffy. Beat in the egg yolks.
Stir in the milk and flour. Whip the egg whites and fold into the mixture.
Pour the mixture into a heatproof bowl and put this bowl in a water bath.
(A water bath is a larger pan containing water in which to place the smaller cake baking pan. This is done to keep the oven moisture high)
Bake at 180 degree C for 45 minutes.
Dust with icing sugar and serve with ice cream.
Key Ingredients: butter, castor sugar, lemon rind, lemon juice, egg, milk, all purpose flour, baking powder