Apex domains cannot have CNAME records.
Question and response
Question
dig 26-0.148.245.62.in-addr.arpa. NS
Answer
26-0.148.245.62.in-addr.arpa. 5 NS ns-1189.awsdns-20.org.
26-0.148.245.62.in-addr.arpa. 5 NS ns-981.awsdns-58.net.
26-0.148.245.62.in-addr.arpa. 5 NS ns-236.awsdns-29.com.
26-0.148.245.62.in-addr.arpa. 5 NS ns-1853.awsdns-39.co.uk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0