These lemon shortbread cookies are buttery, tender, zesty, tangy, and (optionally) filled with gooey lemon curd. They have a melt in your mouth texture. They're packed full of lemon flavor even without the lemon curd! The shortbread cookies come together very quickly and easily - and turn out super buttery and tender crisp. They’re dipped in a two ingredient lemon glaze and are the perfect holiday and summer cookie.