First - oven to 180c. 

Cream softened butter and sugar well. Add 2 eggs beating the first one in well before adding the second and beating that one in too. Add sifted cornflour and beat for 5 minutes. Lastly fold in baking powder and lemon essence.

Line a 9" by 7" tin with baking paper and bake for 1 hour.

The icing we used was Butter Icing from the Edmonds Cookbook. (Editors Note - try the Tangy Butter Icing if you don't have Edmonds).