Ginny insists this wasn't her best batch and her tin was too small, but it looks pretty good to us.

8 ounces unsalted butter, softened
2 1/2 ounces icing sugar
9 ounces plain flour
14 ounces granulated sugar
4 medium eggs, beaten together
4 tablespoons plain flour
1 teaspoon baking powder
Grated zest 2 lemons
6 tablespoons lemon juice, strained
Confectioner’s sugar for dusting

1 Put the softened butter in the bowl of a food processor and process until whipped, then add the icing sugar and process until light in colour (creamed). Sprinkle the flour over and process until the mixture starts to form a ball. Tip into a non-stick jelly roll pan (32 cm x 21 cm), with the bottom lined with parchment paper, and press flat. If the mixture is sticky, keep your fingers dusted with plain flour.

2 Bake in an oven preheated to 170°C (regular) for 15 minutes, then remove from the oven. While the base is cooling, make the topping.

3 Tip the granulated sugar into the bowl of a food processor and pour in the eggs. Process for 1 minute. Transfer the mixture to a bowl, then sprinkle the flour and baking powder over, and add the lemon zest and juice. Mix together with a large spoon.

4 Pour the mixture on top of the base (it will fill the tin), then return it to the oven and bake for a further 30-35 minutes, or until golden in colour and firmish to the touch. Cool in the tin, then dust with superfine confectioner’s sugar and cut into squares. Transfer to an airtight container when cool.

Tips This super-delectable, sweet-but-tart 'slice' is quickly made in a food processor. If you don’t have a food processor, cream the butter and icing sugar and work in the flour. For the topping, whip the sugar and eggs together with a rotary beater.

Recipe by Julie Biuso.