Step 1

Grease a 20cm square cake pan and line with baking paper. Use electric beaters to beat the butter, sugar and vanilla in a bowl until pale and creamy. Beat in the egg. Fold through the flour. Press into the base of the tin. Place in the fridge for 1 hour, to rest.

Step 2

Preheat oven to 180C/160C fan forced. Bake the base for 25 minutes or until golden. Set aside to cool.

Step 3

For the topping, use electric beaters to beat the sugar, eggs, yolks, lemon rind and lemon juice in a bowl. Fold through the flour.

Step 4

Pour over the base. Bake for 30 minutes or until firm. Cool in pan. Place in the fridge to firm. Sprinkle with icing sugar. Cut into squares and top with peel, if using.