Apex domains cannot have CNAME records.
Question and response
Question
dig correioseguro.com.br. NS
Answer
correioseguro.com.br. 4 NS ns-1484.awsdns-57.org.
correioseguro.com.br. 4 NS ns-937.awsdns-53.net.
correioseguro.com.br. 4 NS ns-130.awsdns-16.com.
correioseguro.com.br. 4 NS ns-1966.awsdns-53.co.uk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0