Apex domains cannot have CNAME records.
Question and response
Question
dig 7.175.210.in-addr.arpa. NS
Answer
7.175.210.in-addr.arpa. 4 NS ns4.odn.ne.jp.
7.175.210.in-addr.arpa. 4 NS ns2.odn.ne.jp.
Authority
The response has no authority records.
Additional
ns2.odn.ne.jp. 4 A 143.90.130.11
ns4.odn.ne.jp. 4 A 143.90.130.166
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0