Whole Lemon Cake with Lemon Cheesecake Icing

Ingredients

• 2 small thin-skinned lemons, or 1 large one
• 275g (10oz) softened butter, plus extra for dusting
• 275g (10oz) caster sugar
• 275g (10oz) self-raising flour
• 2 level tsp baking powder
• 4 eggs
• 50g (2oz) softened butter
• 175g (6oz) icing sugar
• 250g (9oz) full-fat mascarpone
• 175g (6oz) fondant icing sugar
• 1 thin-skinned lemon
• 50g (2oz) caster sugar