Lemon and elderflower ombre cake

Name: Lemon and elderflower ombre cake
Prep time: 2 h 30 min
Cook time: 5 h 30 min
Total time: 5 h 30 min
Yield: 24 portions
Ingredients: unsalted butter; ½ lemon; 200 g caster sugar; 225 g unsalted butter; 4 eggs; 3 tbsp elderflower cordial; 225 g self-raising flour; 3 pinches ground turmeric; unsalted butter; ½ lemon; 200 g caster sugar; 225 g unsalted butter; 4 eggs; 3 tbsp elderflower cordial; 225 g self-raising flour; 2 tsp ground turmeric; 40 g lemon juice; 70 g caster sugar; 80 g unsalted butter; 2 eggs; 500 g unsalted butter; 700 g icing sugar; 1 tbsp pouring (whipping) cream; 2 tsp elderflower cordial; 1 ¼ tsp ground turmeric