Pre-heat the oven to 180°C / Gas Mark 4.
Line an 18cm/7inch loaf tin with oiled greaseproof paper.
Beat the 170g butter, WHITWORTHS CASTER SUGAR and vanilla for 2-3 minutes or until it is light and fluffy.
Add the eggs and lemon zest and continue to beat for 2-3 minutes.
Add the juice of half a lemon, milk and beat to combine.
Add the flour and gently mix to combine thoroughly.
Spoon the mixture into the tin and tap the cake tin gently a few times on the counter top to flatten out the top.
Bake for 45-50 minutes or until a skewer comes out clean.
Meanwhile, gently heat the remaining lemon juice and 80g of WHITWORTHS CASTER SUGAR in a small pan to dissolve and allow to reduce to a syrupy consistency over a medium heat for 2-3 minutes.
Remove the cake from the oven and prick all over with a fork.
Carefully spoon the hot lemon syrup over the cake and finally sprinkle over the WHITWORTHS DEMERARA SUGAR.
Leave the cake in the tin for 20-30 minutes to allow the syrup to settle.
Remove the cake from the tin onto a wire rack and allow to cool completely before serving.