Apex domains cannot have CNAME records.
Question and response
Question
dig america-net.com.br. NS
Answer
america-net.com.br. 5 NS ns4.america-net.com.br.
america-net.com.br. 5 NS ns1.america-net.com.br.
america-net.com.br. 5 NS ns2.america-net.com.br.
america-net.com.br. 5 NS ns3.america-net.com.br.
Authority
The response has no authority records.
Additional
ns1.america-net.com.br. 5 A 186.225.127.171
ns2.america-net.com.br. 5 A 186.225.127.172
ns3.america-net.com.br. 5 A 186.225.127.173
ns4.america-net.com.br. 5 A 186.225.127.174
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0