Ingredients:

300g plain flour (you might need less than 300g)
100g butter, softened
1 tsp baking powder
1 tsp vanilla extract
100g of caster sugar
1 egg
Zest of 3 lemons
Juice of ½ lemon
Icing sugar (for coating) 

Method:

Preheat the oven to 180°C. Line a baking sheet with foil or parchment paper

Stir together the butter, egg, sugar, vanilla extract, zest and lemon juice into a bowl using a wooden spoon and mix well

Sift the baking powder and add to the butter and egg mix

Sift the flour over the mix little by little with a wooden spoon until you have a soft and sticky dough (you may need less than 300g of flour)

Roll biscuit dough into balls or long sausages keeping your hands wet (the dough will be very sticky!!!) to obtain about 20 biscuits

Roll each biscuit into the icing sugar

Place the biscuit balls onto the baking tray, leaving a some space between each one

Bake for approximately 20-25 minutes or until pale golden