Step 1

Preheat oven to 170C. Line an 18cm x 25cm slice tin with baking paper.

Step 2

Whisk egg whites until stiff. Set aside.

Step 3

Whisk egg yolks with sugar, pudding mix and melted butter until pale. Whisk in flour, ensuring there are no lumps. Add milk, lemon juice and lemon zest and whisk until smooth. Fold through beaten egg whites, being careful not to overmix at this stage. Pour into prepared tin. Bake for 25 minutes until just set.

Step 4

Allow to cool, then slice into squares, dust with icing sugar and serve.