Rotate the lemon just as the white pith appears, but avoid grating the white pith since it’s bitter. If you don’t have a zester or a grater, you can zest a lemon using just a small knife.

For the icing, begin by removing the zest from the lemon - it's best to use a zester to get long, curly strips. Then sift the icing sugar into a bowl and gradually stir in the lemon juice until ...