Equipment

• Heat the oven to 180C/160C fan/gas 4. Butter a 30cm x 20cm deep baking dish.
• Put all of the butter and 250g of the caster sugar in a bowl and whisk for 5 mins until pale and fluffy. Add the eggs and whisk, then sieve over the flour and baking powder and gently mix in until you have a batter. Alternatively, do all of this with a whisk or mixer. Stir in the lemon zest, reserving a little for decoration.
• Spoon the sponge batter into the dish and smooth over the top.
• Mix the lemon juice with the cornflour in a heatproof bowl to make a smooth paste. Mix the remaining 130g caster sugar with 300ml boiling water in a jug, pour over the cornflour mix and whisk until smooth. Pour this over the sponge. Bake for 45-50 mins until golden and set, and the sponge springs back when touched.
• While the pudding is baking, make the lemon drizzle. Mix the icing sugar with enough lemon juice (about half of it) to create a loose consistency. Drizzle over the sponge while it’s still warm and decorate with the reserved lemon zest. Serve straightaway with cream or custard.