Pre-heat your oven to 180°c (160°c for fan assisted ovens or Gas Mark 4) and line a 2lb loaf tin with some greaseproof paper. Set aside.
In a large bowl, sift the flour over the butter, caster sugar, eggs, milk and zest of your lemon. Mix well until all the ingredients are combined and smooth.
Transfer to your pre-lined tin and bake for 45-50 minutes, until golden on top and skewer inserted comes out clean.
Allow to cool in the tin for 5 minutes before poking the top of your cake all over with a skewer.
In a small bowl, mix half the icing sugar with the juice of your lemon to create a syrup-like icing, and spoon half of the syrup all over the cake.
Add the other half of icing sugar to the remaining syrup to create a thin icing. Spoon over the top whilst the cake is still warm to finish with an icing glaze.
If desired, top with a little extra lemon zest.