Place a rack in middle of oven; preheat to 350°F.
In a food processor, pulse all ingredients until mixture begins to form small lumps. Sprinkle mixture into a 13x9x2-inch baking pan and with a metal spatula press evenly onto bottom. Bake shortbread until golden, about 20 minutes. While shortbread is baking, prepare lemon filling.
In a large bowl whisk together eggs and granulated sugar until combined well and stir in lemon juice and flour. Pour lemon mixture over hot shortbread. Reduce oven temperature to 300°F and bake confection in middle of oven until set, about 30 minutes. Cool completely in pan and cut into 24 bars. Sift confectioners' sugar over bars before serving. Do Ahead: Bar cookies keep, covered and chilled, 3 days.
Editor's Note: This recipe was originally published in the October 1999 issue of ‘Gourmet’ and first appeared on Epicurious in August 2004. For more of our favorite classic ‘Gourmet’ dessert recipes, head this way→
