Cut butter into flour until the size of small peas. Beat eggs and add with sugar, lemon juice and peel. Save out 1 cup of this dough. Roll out remaining dough to fit bottom and side of a greased 9x13" pan. Spread the dough with apricot preserves. Chill while preparing filling. Filling: Mix egg yolks with sugar; add nuts. Beat egg whites until stiff. Carefully fold in nut mixture. Spread over apricots. Roll out saved dough. Cut in 1/2" strips to form a diagonal lattice on top of filling. Bake at 350'F. 60-75 minutes until golden.