Apex domains cannot have CNAME records.
Question and response
Question
dig m9network.com. NS
Answer
m9network.com. 5 NS ns3.supramail.com.br.
m9network.com. 5 NS ns2.m9.network.
m9network.com. 5 NS ns1.m9.network.
m9network.com. 5 NS ns4.supramail.com.br.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0