Apex domains cannot have CNAME records.
Question and response
Question
dig 72.75.177.in-addr.arpa. NS
Answer
72.75.177.in-addr.arpa. 4 NS ns-rev-02.tely.com.br.
72.75.177.in-addr.arpa. 4 NS ns-rev-01.tely.com.br.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0