Apex domains cannot have CNAME records.
Question and response
Question
dig networktelecomunicacoes.com.br. NS
Answer
networktelecomunicacoes.com.br. 5 NS ns02.networktelecomunicacoes.com.br.
networktelecomunicacoes.com.br. 5 NS ns01.networktelecomunicacoes.com.br.
Authority
The response has no authority records.
Additional
ns01.networktelecomunicacoes.com.br. 5 A 189.1.176.252
ns02.networktelecomunicacoes.com.br. 5 A 189.1.176.253
ns01.networktelecomunicacoes.com.br. 5 AAAA 2804:4:0:6:0:0:176:252
ns02.networktelecomunicacoes.com.br. 5 AAAA 2804:4:0:6:0:0:176:253
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0