Apex domains cannot have CNAME records.
Question and response
Question
dig texnet.net.br. NS
Answer
texnet.net.br. 5 NS ns1.texnet.net.br.
texnet.net.br. 5 NS ns2.texnet.net.br.
Authority
The response has no authority records.
Additional
ns1.texnet.net.br. 5 A 138.36.0.70
ns2.texnet.net.br. 5 A 168.232.85.22
ns1.texnet.net.br. 5 AAAA 2804:2190:fff0:1111:0:0:0:0
ns2.texnet.net.br. 5 AAAA 2804:2190:fff0:0:168:232:85:22
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0