Frosted courgette & lemon cake

INGREDIENTS

• 250g pack unsalted butter , very soft, plus extra for the tin
• 3 unwaxed lemons
• 200g golden caster sugar
• 3 eggs
• 2 medium courgettes , coarsely grated (you'll need 300g/10oz flesh)
• 1 tsp poppy seeds , plus extra to decorate
• 1 tsp vanilla extract
• 100g self-raising flour
• 100g plain wholemeal flour
• 1 tsp baking powder
• 85g icing sugar
• 200g pack full-fat soft cheese
• 4 tbsp lemon curd (optional)