Apex domains cannot have CNAME records.
Question and response
Question
dig s3.us-west-2.amazonaws.com. NS
Answer
s3.us-west-2.amazonaws.com. 5 NS ns-1065.awsdns-05.org.
s3.us-west-2.amazonaws.com. 5 NS ns-183.awsdns-22.com.
s3.us-west-2.amazonaws.com. 5 NS ns-1003.awsdns-61.net.
s3.us-west-2.amazonaws.com. 5 NS ns-1696.awsdns-20.co.uk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0