Apex domains cannot have CNAME records.
Question and response
Question
dig virtuaserver.com.br. NS
Answer
virtuaserver.com.br. 5 NS ns5.virtuaserver.com.br.
virtuaserver.com.br. 5 NS ns2.virtuaserver.com.br.
virtuaserver.com.br. 5 NS ns4.virtuaserver.com.br.
Authority
The response has no authority records.
Additional
ns2.virtuaserver.com.br. 5 A 204.188.217.209
ns4.virtuaserver.com.br. 5 A 51.222.29.152
ns5.virtuaserver.com.br. 5 A 149.202.59.230
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0