Preheat the oven to 180 degrees C and lightly grease a loose-bottomed tart tin.
Add all the ingredients to a food processor and process until it comes together to form a dough.
Place the dough in the tart tin and flatten it out evenly to fill the tin. Prick it all over with a fork.
Bake 20 minutes or until golden brown. Slice it into wedges while still warm, then let cool in the tin until cool enough to handle. Push up the base of the tin and transfer the shortbread to a wire rack to cool all the way.
No food processor?
You can also make this easy recipe by hand - just cream the butter and sugar together until light and fluffy then mix in the other ingredients by hand to form a dough.