Apex domains cannot have CNAME records.
Question and response
Question
dig 110.128.in-addr.arpa. NS
Answer
110.128.in-addr.arpa. 5 NS ns5.utah.edu.
110.128.in-addr.arpa. 5 NS ns.utah.edu.
110.128.in-addr.arpa. 5 NS fiber.utah.edu.
110.128.in-addr.arpa. 5 NS ns6.utah.edu.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0