Apex domains cannot have CNAME records.
Question and response
Question
dig infortel.net.br. NS
Answer
infortel.net.br. 5 NS ns1.infortel.net.br.
infortel.net.br. 5 NS ns2.infortel.net.br.
Authority
The response has no authority records.
Additional
ns1.infortel.net.br. 5 A 186.226.160.235
ns2.infortel.net.br. 5 A 186.226.161.235
ns1.infortel.net.br. 5 AAAA 2804:2ab8:186:226:160:0:0:235
ns2.infortel.net.br. 5 AAAA 2804:2ab8:186:226:161:0:0:235
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0