Apex domains cannot have CNAME records.
Question and response
Question
dig redebrasil.com.br. NS
Answer
redebrasil.com.br. 4 NS ns2.redebrasil.com.br.
redebrasil.com.br. 4 NS ns3.redebrasil.com.br.
Authority
The response has no authority records.
Additional
ns2.redebrasil.com.br. 4 A 186.201.42.130
ns3.redebrasil.com.br. 4 A 200.225.50.98
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0