Apex domains cannot have CNAME records.
Question and response
Question
dig algartecnologia.com.br. NS
Answer
algartecnologia.com.br. 5 NS ns-1773.awsdns-29.co.uk.
algartecnologia.com.br. 5 NS ns-1481.awsdns-57.org.
algartecnologia.com.br. 5 NS ns-39.awsdns-04.com.
algartecnologia.com.br. 5 NS ns-808.awsdns-37.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0