Apex domains cannot have CNAME records.
Question and response
Question
dig 64.89.160.114.in-addr.arpa. NS
Answer
64.89.160.114.in-addr.arpa. 4 NS ns2.ict-24cloud.com.
64.89.160.114.in-addr.arpa. 4 NS ns.ict-24cloud.com.
64.89.160.114.in-addr.arpa. 4 NS ns-tk011.ocn.ad.jp.
Authority
The response has no authority records.
Additional
ns.ict-24cloud.com. 4 A 114.160.89.66
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0