Apex domains cannot have CNAME records.
Question and response
Question
dig mzweb.com.br. NS
Answer
mzweb.com.br. 5 NS ns-552.awsdns-05.net.
mzweb.com.br. 5 NS ns-171.awsdns-21.com.
mzweb.com.br. 5 NS ns-1722.awsdns-23.co.uk.
mzweb.com.br. 5 NS ns-1078.awsdns-06.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0