Preheat the oven to 180 degrees C. Lightly flour a 25.5 x 30 cm baking tray.
If you have a food processor: Place the flour, almonds, butter, sugar and lemon zest in the bowl then mix until it all comes together.
If you are making it by hand: Cream the butter and sugar together until it is light and fluffy. Sift the flour and almonds into the mixture, then mix it together with your hands until the dough comes together.
Place the mixture in the tray and spread it out evenly.
Bake for 20 minutes or until golden brown. Mark the shortbread into squares while it is still soft, then leave to cool in the tray for about 10 to 15 minutes. Then transfer to a wire cooling rack to cool completely.