Apex domains cannot have CNAME records.
Question and response
Question
dig chrtelecom.net.br. NS
Answer
chrtelecom.net.br. 4 NS ns1.chrtelecom.net.br.
chrtelecom.net.br. 4 NS controllr.chrtelecom.net.br.
chrtelecom.net.br. 4 NS sip.chrtelecom.net.br.
chrtelecom.net.br. 4 NS dns-2a.chrtelecom.net.br.
chrtelecom.net.br. 4 NS grafico.chrtelecom.net.br.
chrtelecom.net.br. 4 NS ns2.chrtelecom.net.br.
Authority
The response has no authority records.
Additional
ns1.chrtelecom.net.br. 4 A 138.0.124.9
ns2.chrtelecom.net.br. 4 A 138.0.124.10
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0