Preheat oven to 325°. In a large bowl, cream butter and confectioners' sugar until smooth. Gradually beat in flour. Press dough onto bottom and up sides of an ungreased 11-in. fluted tart pan with removable bottom. Refrigerate 15 minutes.
Line the unpricked crust with a double thickness of foil. Fill with pie weights, dried beans or uncooked rice. Bake until edges are lightly browned, 18-22 minutes. Remove foil and weights; bake until bottom is golden brown, 5-7 minutes longer. Cool on a wire rack.
In a large bowl, beat sugar, lemon zest, lemon juice, eggs, egg yolks, cream cheese and cornstarch until blended; pour into crust. Bake until filling is set, 18-22 minutes. Cool on a wire rack. If desired, serve with whipped cream. Refrigerate leftovers.
Editor's Note Let pie weights cool before storing. Beans and rice may be reused for pie weights, but not for cooking.