Preheat the oven to 180 degree, 10 minutes before baking. Lightly oil and line the base of an 18 cm/7 inch square cake tin with baking paper. In a large bowl, cream the butter and sugar together until soft and fluffy.
Beat the eggs, then gradually add a little of the egg to the creamed mixture, adding 1 tablespoon of flour after each addition.
Finely grate the rind from one of the lemons and stir into the creamed mixture, beating well until smooth.
Squeeze the juice from the lemon, strain, then stir into the mixture.
Spoon into the prepared tin, level the surface and bake in the preheated oven for 25-30 minutes.
Mix the zest of the last lemon with 25 gm of the granulated sugar and reserve.
Squeeze the juice of that lemon into a saucepan. Add the rest of the granulated sugar to the lemon juice and heat gently, stirring occasionally. When the sugar has dissolved simmer gently for 3-4 minutes until syrupy.
With a fine skewer prick the cake all over. Sprinkle the lemon zest and sugar over the top of the cake, drizzle over the syrup and leave to cool in the tin. Cut the cake into squares and serve.
Notes
Substitution for Self-raising flour: Take 175 gms all-purpose (plain) flour and add2 1/4 tsp baking powder and a pinch of salt. Sift or whisk together well, and proceed to use this mixture in place of the self-raising flour.Substitution for Caster sugar: process 175 gms granulated sugar (regular sugar) in a food processor/mixer until fine, but don't powder it like icing sugar.