Apex domains cannot have CNAME records.
Question and response
Question
dig multiplicnet.com.br. NS
Answer
multiplicnet.com.br. 4 NS ns1.valueserver.com.br.
multiplicnet.com.br. 4 NS ns4.valueserver.com.br.
multiplicnet.com.br. 4 NS ns3.valueserver.com.br.
multiplicnet.com.br. 4 NS ns2.valueserver.com.br.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0