Preheat the oven to 180C/350F/gas mark 4
Use a 20cm/8 inch round cake tin.
Grease and base line the tin. Sift together the flour and salt. Add the butter, caster sugar, yoghurt and lemon rind and beat until smooth and thick. Spoon the mixture into the tin and level the surface. Bake for about 11/4 hours, or until the cake is risen, firm to the touch and shrinking from the sides of the tin. Allow to firm up in the tin for 5 minutes, then turn out onto a wire tray.
Icing and decoration: Pour the lemon juice into the icing sugar to achieve a spreadable icing. Take care not to add too much juice as it is very easy to make the icing too thin. Spread the icing on the cooled cake. Cut the pared rind into the thinnest strips you can. Put the strips into a small pan with water just to cover. Bring to the boil and drain, then cover with fresh water. Stir in the sugar and boil for 1 - 2 minutes until the peel is soft. Drain the peel in a sieve and cool under the cold tap. Pat it dry on kitchen paper and scatter on top of the icing.
