Preheat the oven to 170°c (150 fan/ Gas 3/ 320F) and grease and line a 2lb (900g) loaf tin with baking paper.
Cream together the butter and sugar in a large mixing bowl with a wooden spoon until pale and fluffy.
180 g Butter, 180 g Golden Caster Sugar
Beat in the eggs one by one to prevent the mixture from curdling, and mix in the lemon zest, lemon juice, and vanilla extract.
3 Eggs, 1 teaspoon Vanilla Extract, 1 Lemon
Fold in the flours and mix until you have a thick smooth batter.
200 g Self Raising Flour, 50 g Plain Flour
Pour the batter into your prepared 2lb loaf tin and bake for 55 minutes - 1 hour, or until a skewer comes out clean. Allow the cake to cool for 15 minutes before running a knife around the edge of the tin and removing it to a wire rack