Apex domains cannot have CNAME records.
Question and response
Question
dig eteccinformatica.com.br. NS
Answer
eteccinformatica.com.br. 5 NS ns1.eteccinformatica.com.br.
eteccinformatica.com.br. 5 NS ns2.eteccinformatica.com.br.
Authority
The response has no authority records.
Additional
ns1.eteccinformatica.com.br. 5 A 177.185.40.18
ns2.eteccinformatica.com.br. 5 A 177.185.40.20
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0