A condemning authority, if acquiring less than the total amount of a single unit of contiguous property, shall, if the remaining portion of such property does not conform to the area requirements of existing zoning regulations, obtain a zoning variance for such remaining portion of property from the local zoning board of appeals before condemning any portion of such property. If such variance is not obtained prior to the taking by the condemning authority, the owner or owners of such single unit of contiguous property shall be reimbursed for the total amount of such unit and the condemning authority shall take title in fee simple to the entire unit of contiguous property.