Apex domains cannot have CNAME records.
Question and response
Question
dig 97.155.in-addr.arpa. NS
Answer
97.155.in-addr.arpa. 1 NS fiber.utah.edu.
97.155.in-addr.arpa. 1 NS ns6.utah.edu.
97.155.in-addr.arpa. 1 NS ns.utah.edu.
97.155.in-addr.arpa. 1 NS ns5.utah.edu.
Authority
The response has no authority records.
Additional
ns.utah.edu. 1 A 128.110.124.120
ns5.utah.edu. 1 A 35.83.221.243
ns6.utah.edu. 1 A 3.20.87.127
fiber.utah.edu. 1 A 128.110.132.99
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0