Apex domains cannot have CNAME records.
Question and response
Question
dig 64.227.125.42.in-addr.arpa. NS
Answer
64.227.125.42.in-addr.arpa. 5 NS ns013-hhvsu7n9lgrv6ql0.h.d-53.jp.
64.227.125.42.in-addr.arpa. 5 NS ns013-hhvsu7n9lgrv6ql0.h.d-53.net.
64.227.125.42.in-addr.arpa. 5 NS ns013-hhvsu7n9lgrv6ql0.h.d-53.info.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0