Cream the butter (margarine will do) and sugar until light and fluffy and add the lemon rind.
Sieve the cornflour and baking powder together.
Break the egg into a bowl and beat with a fork.
Add a small amount (about a tablespoon) of egg and a similar amount of cornflour alternately to the creamed butter and sugar, beating well between each addition.
Place about a dozen paper cake cases in a baking tin and add a teaspoonful of mixture to each case
Use the back of another spoon to push it off.
Place in a pre-heated oven at 375F/180C/Gas mark 4 and bake for 10 minutes, until firm and golden
Don't let them get beyond a golden colour.
Allow the cakes to cool on a rack and then add a dusting of the icing sugar.