Lemon Shortbread Squares

I love the sharp citrus tang of these, with the crumbly buttery shortbread underneath. A little like a lemon tart, but in cake / biscuit form.

1. 1

   Preheat the oven to 170 degrees C.
   Line the base and sides of a 20cm square baking tin with foil or baking paper, with an overhang on two opposite sides, and rub a little extra butter on the lined base.
   Cut the cold butter into cubes. Sift the 210 g flour and 60 g icing sugar into the food processor, add the cubed butter and pulse until it resembles breadcrumbs and is moist to touch.
   Tip the crumbly dough into the prepared tin and press flat with your hands. Prick the base a few times with a fork. Bake for 25 minutes, until lightly golden, then remove from the oven but leave it on at the same temperature.
   With an electric hand whisk, or in a stand mixer, beat together the lemon juice, lemon zest, caster sugar and eggs for about a minute, then sift in the flour and baking powder and whisk for a few seconds to combine.
   Pour over the base (no need to leave it to cool) and return to the oven for another 20 to 25 minutes, until the lemon topping has set with just a little wobble in the middle.
   Leave in the tin until completely cooled, then lift them out with the help of the foil / paper. Dust with icing sugar, then cut into 16 squares.