Sweet and tart with a slightly nutty finish, these Pistachio Lemon Shortbread Bars are the perfect combination of all your favorite sweets. The buttery shortbread crust gets an upgrade from punchy green pistachios while the tangy lemon curd and powdered sugar topping create a perfect balance. These are perfect cold or at room temperature and are easy to take along to picnics, barbecues, and bake sales.