Apex domains cannot have CNAME records.
Question and response
Question
dig supramail.com.br. NS
Answer
supramail.com.br. 5 NS kes.supramail.com.br.
supramail.com.br. 5 NS tuvok.supramail.com.br.
supramail.com.br. 5 NS sisko.supramail.com.br.
supramail.com.br. 5 NS chakotay.supramail.com.br.
Authority
The response has no authority records.
Additional
kes.supramail.com.br. 5 A 51.222.15.118
sisko.supramail.com.br. 5 A 149.56.175.114
tuvok.supramail.com.br. 5 A 205.251.199.141
chakotay.supramail.com.br. 5 A 201.16.160.2
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0