Apex domains cannot have CNAME records.
Question and response
Question
dig 160-27.30.4.62.in-addr.arpa. NS
Answer
160-27.30.4.62.in-addr.arpa. 5 NS ns-1048.awsdns-03.org.
160-27.30.4.62.in-addr.arpa. 5 NS ns-1835.awsdns-37.co.uk.
160-27.30.4.62.in-addr.arpa. 5 NS ns-54.awsdns-06.com.
160-27.30.4.62.in-addr.arpa. 5 NS ns-778.awsdns-33.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0