Apex domains cannot have CNAME records.
Question and response
Question
dig highspeed2.net.br. NS
Answer
highspeed2.net.br. 5 NS ns1.highspeed2.net.br.
highspeed2.net.br. 5 NS ns2.highspeed2.net.br.
Authority
The response has no authority records.
Additional
ns1.highspeed2.net.br. 5 A 200.124.67.231
ns2.highspeed2.net.br. 5 A 200.124.65.227
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0