Apex domains cannot have CNAME records.
Question and response
Question
dig voope.com.br. NS
Answer
voope.com.br. 5 NS ns1.voope.com.br.
voope.com.br. 5 NS ns3.voope.com.br.
voope.com.br. 5 NS ns2.voope.com.br.
Authority
The response has no authority records.
Additional
ns1.voope.com.br. 5 A 189.14.224.189
ns2.voope.com.br. 5 A 189.14.224.190
ns3.voope.com.br. 5 A 200.98.64.90
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0