Pre-heat the oven to 150C Fan/325F/Gas Mark 3 and grease and line a 2lb loaf tin
Mix together the butter or baking spread and caster sugar until light and fluffy, around 3 minutes, ideally using an electric mixer
Add the eggs and whisk in until smooth
Mix in the flour gently until fully combined, then mix in the lemon zest
Pour the mixture into the loaf tin and bake for an hour, or until a skewer inserted in the centre comes out clean
While the cake is baking, juice the lemons that you zested for the cake. Mix the juice with the granulated sugar and set aside.
When the cake is done, but still warm, poke it all over with a thin skewer or cocktail stick. Brush or spoon the lemon and sugar mixture over it. Then leave the cake to cool fully in the tin
To make the icing, mix the lemon juice and icing sugar together. Remove the cake from the tin and remove the baking paper, put it on your serving plate. Drizzle or pipe the icing over the cake. Then add the lemon zest on top if you like
Store in an airtight container in a cool place and eat within 3 days. Or you can freeze it for up to 3 months