Sift the flour & baking powder into a large bowl

Add the butter and rub it with your fingertips until the mixture resembles fine breadcrumbs

Stir the sugar and lemon zest into the mixture, add the eggs and combine to form a soft dough

Turn the mixture out on to a lightly floured work surface and divide the dough in half

Shape each piece of dough into a log shape about 3cm/1¼inches in diameter

Wrap each log in baking paper and then in foil and chill in the refrigerator for at least 8 hours or until required (I put one of the logs in the freezer to use at a later date)

Preheat the oven to 190ºC/375ºF/Gas mark 5

Grease a large baking sheet (or a few if you're making a big batch)

Slice the dough into as many 8mm/⅜-inch slices as required

Place the slices on the baking sheet, spaced well apart

Return any remaining dough to the fridge for up to a week

Bake in the preheated oven for 10-15 minutes or until golden brown

Leave on the baking sheet to cool slightly for 2-3 minutes before transferring to cool completely