Apex domains cannot have CNAME records.
Question and response
Question
dig brava.inf.br. NS
Answer
brava.inf.br. 5 NS ns2.brava.inf.br.
brava.inf.br. 5 NS ns1.brava.inf.br.
Authority
The response has no authority records.
Additional
ns1.brava.inf.br. 5 A 186.235.83.6
ns2.brava.inf.br. 5 A 186.235.80.6
ns1.brava.inf.br. 5 AAAA 2804:984:80:88:0:0:0:6
ns2.brava.inf.br. 5 AAAA 2804:984:80:8a:0:0:0:6
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0