Cream butter and sugar and add eggs one at a time. Mix thoroughly. Fold in remaining ingredients and bake at 160 degrees for an hour.
For the lemon buttercream, mix 100g softened butter, 200g icing sugar, 1 tablespoon lemon rind and 100g cream cheese. Add 1-2 tbsp water to thin the icing down if too thick (it will pull the cake and you will end up with crumbs all through the icing).