Apex domains cannot have CNAME records.
Question and response
Question
dig pointermail.com.br. NS
Answer
pointermail.com.br. 2 NS ns-502.awsdns-62.com.
pointermail.com.br. 2 NS ns-1813.awsdns-34.co.uk.
pointermail.com.br. 2 NS ns-1375.awsdns-43.org.
pointermail.com.br. 2 NS ns-997.awsdns-60.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0