Apex domains cannot have CNAME records.
Question and response
Question
dig arbexti.com.br. NS
Answer
arbexti.com.br. 5 NS ns1.186-209-113-106.cprapid.com.
arbexti.com.br. 5 NS ns2.186-209-113-106.cprapid.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0