Apex domains cannot have CNAME records.
Question and response
Question
dig 192h.92.186.106.in-addr.arpa. NS
Answer
192h.92.186.106.in-addr.arpa. 5 NS c.ns.192h.92.186.106.in-addr.arpa.
192h.92.186.106.in-addr.arpa. 5 NS e.ns.192h.92.186.106.in-addr.arpa.
192h.92.186.106.in-addr.arpa. 5 NS a.ns.192h.92.186.106.in-addr.arpa.
192h.92.186.106.in-addr.arpa. 5 NS f.ns.192h.92.186.106.in-addr.arpa.
192h.92.186.106.in-addr.arpa. 5 NS a.ns.cheetahmail.com.
192h.92.186.106.in-addr.arpa. 5 NS d.ns.cheetahmail.com.
192h.92.186.106.in-addr.arpa. 5 NS b.ns.cheetahmail.com.
192h.92.186.106.in-addr.arpa. 5 NS e.ns.cheetahmail.com.
192h.92.186.106.in-addr.arpa. 5 NS b.ns.192h.92.186.106.in-addr.arpa.
192h.92.186.106.in-addr.arpa. 5 NS d.ns.192h.92.186.106.in-addr.arpa.
192h.92.186.106.in-addr.arpa. 5 NS c.ns.cheetahmail.com.
192h.92.186.106.in-addr.arpa. 5 NS f.ns.cheetahmail.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0