Apex domains cannot have CNAME records.
Question and response
Question
dig altovalenet.com.br. NS
Answer
altovalenet.com.br. 4 NS ns.altovalenet.com.br.
altovalenet.com.br. 4 NS ns2.altovalenet.com.br.
Authority
The response has no authority records.
Additional
ns.altovalenet.com.br. 4 A 177.84.0.2
ns2.altovalenet.com.br. 4 A 177.84.0.3
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0