Apex domains cannot have CNAME records.
Question and response
Question
dig 232.0.168.in-addr.arpa. NS
Answer
232.0.168.in-addr.arpa. 5 NS ns-rev-02.tely.com.br.
232.0.168.in-addr.arpa. 5 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