1. Heat oven to 170C. Cream together butter and icing sugar. Then add flour. Press into a greased and lined sponge roll tin. Bake for 15 minutes.
2. Meanwhile make the topping. Beat sugar and eggs together until creamy and thick. Mix in lemon zest, flour, baking powder, and lemon juice. Stir until smooth.
3. Pour mixture over partly cooked base and cook a further 30 minutes or until golden and slightly firm.
4. Cool in the tin and cut into 24 pieces (less for bigger serves). Serve sprinkled with icing sugar or with aspoonful of lemon yoghurt for dessert.

See MgairieM Phillips' original recipe in the Reader Recipe section.