Before approving any subdivision variance, the Board of County Commissioners shall hold a public hearing thereon. Notice of such hearing shall be mailed, posted and published in a newspaper of general circulation in the County at least thirty (30) days in advance of the public hearing. Notice of such hearing shall be posted on the property for which the variance is sought and shall be mailed to the owner of such property and to the owners of real property lying within three hundred (300) feet of the exterior boundaries of such property by first class mail, with postage prepaid. The word "owner," as used in this Section, shall be construed to mean persons who are shown to be the record owners of the property upon the records of the Pueblo County Assessor. The purchaser under a bona fide recorded contract of purchase shall be considered the owner for the purposes hereof. Proof of compliance with this Section shall be the written statement of the County Zoning Administrator giving the names and addresses of the persons to whom the notice was mailed and the date of mailing, a statement that the required sign was posted upon such property, and the publisher’s affidavit of publication. Such proof shall be filed with and shall become a part of the record of action taken by the Board of County Commissioners.