Apex domains cannot have CNAME records.
Question and response
Question
dig krypton.com.br. NS
Answer
krypton.com.br. 1 NS ns-1095.awsdns-08.org.
krypton.com.br. 1 NS ns-726.awsdns-26.net.
krypton.com.br. 1 NS ns-349.awsdns-43.com.
krypton.com.br. 1 NS ns-2042.awsdns-63.co.uk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0