Apex domains cannot have CNAME records.
Question and response
Question
dig 32-63.233.188.210.in-addr.arpa. NS
Answer
32-63.233.188.210.in-addr.arpa. 4 NS ns3.pi-pe.co.jp.
32-63.233.188.210.in-addr.arpa. 4 NS ns.pi-pe.co.jp.
Authority
The response has no authority records.
Additional
ns.pi-pe.co.jp. 4 A 210.188.229.230
ns3.pi-pe.co.jp. 4 A 112.137.190.253
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0