Step 1

Preheat oven to 180C/160C fan forced. Grease a 21cm (base size) square cake pan and line with baking paper, allowing the paper to overhang the sides.

Step 2

Use electric beaters to beat the caster sugar and butter in a bowl until pale and creamy. Add the lemon rind and beat until combined. Add eggs, 1 at a time, beating well after each addition. Combine the milk and lemon juice in a jug (don’t worry if it looks a bit curdled). Fold half the flour, then the milk mixture, into the butter mixture. Fold in the remaining flour.

Step 3

Spoon into the prepared pan. Smooth the surface. Bake for 15 minutes. Sprinkle with the white sugar. Bake for a further 15 minutes or until slice springs back when lightly touched.

Step 4

Set aside in the pan for 10 minutes before transferring to a wire rack to cool completely. Cut into squares to serve.