Apex domains cannot have CNAME records.
Question and response
Question
dig onlinetelecomip.net.br. NS
Answer
onlinetelecomip.net.br. 2 NS ns1151.hostgator.com.br.
onlinetelecomip.net.br. 2 NS ns1150.hostgator.com.br.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0