The Best Lemon Bars Ingredients For the Crust 1/2 cup unsalted butter (1 stick), very soft 1 cup all-purpose flour 1/4 heaping cup confectioners' sugar 1 tablespoon cornstarch pinch salt, optional and to taste For the Filling 2 large eggs 1 cup granulated sugar 1/2 cup lemon juice, or to taste (about 2 juicy