Apex domains cannot have CNAME records.
Question and response
Question
dig virtex.com.br. NS
Answer
virtex.com.br. 5 NS dns2.virtex.com.br.
virtex.com.br. 5 NS dns1.virtex.com.br.
Authority
The response has no authority records.
Additional
dns1.virtex.com.br. 5 A 177.66.114.3
dns2.virtex.com.br. 5 A 177.66.116.59
dns1.virtex.com.br. 5 AAAA 2804:ad8:0:0:0:0:0:103
dns2.virtex.com.br. 5 AAAA 2804:ad8:0:0:0:0:0:d
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0