Mix butter, egg yolks, baking soda, baking powder, sugar and flour. Mix lemon peel with sour cream and add to dough, knead until dough leaves hand. Beat egg whites till stiff peaks, fold in nuts, with sugar to taste. Separate dough into 3 balls. Roll one ball of dough out, put in 10 x 15 pan. Spread with the nut filling. Roll second ball of dough out and place on top of nut filling. Spread the apricot filling on top. Roll out final ball of dough and place on top of apricot filling. Prick top with fork. Brush with egg wash and sprinkle of sugar and bake 350F for 30 to 45 minutes. Cut into diamond patterns.