A spouse or domestic partner may make and execute powers of attorney for the sale, conveyance, transfer or encumbrance of his or her separate estate both real and personal, without the other spouse or other domestic partner joining in the execution thereof. Such power of attorney shall be acknowledged and certified in the manner provided by law for the conveyance of real estate. Nor shall anything herein contained be so construed as to prevent either spouse or either domestic partner from appointing the other his or her attorney-in-fact for the purposes provided in this section.