Apex domains cannot have CNAME records.
Question and response
Question
dig 224-255.229.186.213.in-addr.arpa. NS
Answer
224-255.229.186.213.in-addr.arpa. 5 NS ns2.wmhost.org.
224-255.229.186.213.in-addr.arpa. 5 NS ns1.wmhost.org.
224-255.229.186.213.in-addr.arpa. 5 NS ns3.wmhost.org.
Authority
The response has no authority records.
Additional
ns1.wmhost.org. 5 A 89.166.51.6
ns2.wmhost.org. 5 A 213.141.123.198
ns3.wmhost.org. 5 A 89.166.51.3
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0