Raspberry and Rhubarb Drizzle Cake with Custard

Name: Raspberry and Rhubarb Drizzle Cake with Custard
Ingredients: 50g (1¾ oz) golden caster sugar; 2 limes, juice and zest only (zest reserved for the sponge); 150g (5½ oz) rhubarb, trimmed and cut into small chunks; 100g (3½ oz) shelled pistachios, ground to a powder using a food processor; 100g (3½ oz) ground almonds; 100g (3½ oz) fine polenta (also known as cornmeal); pinch of salt; 1½ tsp gluten-free baking powder; 200g (7 oz) unsalted butter; 200g (7 oz) golden caster sugar; 5 large free-range eggs; 200g (7 oz) raspberries; 300ml (10 fl oz) double cream; 50ml (2 fl oz) full-fat milk; 1 tsp vanilla bean paste; 2 large free-range egg yolks; 25g (1 oz) golden caster sugar; 50g (1¾ oz) white caster sugar; 1 large free-range egg white; 100g (3½ oz) raspberries; 1 bunch fresh mint, leaves picked and chopped; 50g (1¾ oz) shelled pistachios; 100g (3½ oz) icing sugar; 1 lime, zest only