Apex domains cannot have CNAME records.
Question and response
Question
dig subnet128.211.62.64.in-addr.arpa. NS
Answer
subnet128.211.62.64.in-addr.arpa. 4 NS ns2.heliohost.org.
subnet128.211.62.64.in-addr.arpa. 4 NS ns1.heliohost.org.
Authority
The response has no authority records.
Additional
ns1.heliohost.org. 4 A 65.19.143.3
ns2.heliohost.org. 4 A 64.62.211.133
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0