Apex domains cannot have CNAME records.
Question and response
Question
dig efit.net.br. NS
Answer
efit.net.br. 4 NS Cp4.americanet.com.br.
efit.net.br. 4 NS Cp3.americanet.com.br.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0