Apex domains cannot have CNAME records.
Question and response
Question
dig oimaisempresas.com.br. NS
Answer
oimaisempresas.com.br. 5 NS ns2cvx.name.com.
oimaisempresas.com.br. 5 NS ns3cqz.name.com.
oimaisempresas.com.br. 5 NS ns4cpw.name.com.
oimaisempresas.com.br. 5 NS ns1cmt.name.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0