Apex domains cannot have CNAME records.
Question and response
Question
dig 192-27.93.18.194.in-addr.arpa. NS
Answer
192-27.93.18.194.in-addr.arpa. 5 NS dns11.se.telia.net.
192-27.93.18.194.in-addr.arpa. 5 NS dns12.se.telia.net.
192-27.93.18.194.in-addr.arpa. 5 NS dns9.telia.com.
192-27.93.18.194.in-addr.arpa. 5 NS dns10.telia.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0