Apex domains cannot have CNAME records.
Question and response
Question
dig s3-w.us-east-2.amazonaws.com. NS
Answer
s3-w.us-east-2.amazonaws.com. 5 NS ns-1505.awsdns-60.org.
s3-w.us-east-2.amazonaws.com. 5 NS ns-509.awsdns-63.com.
s3-w.us-east-2.amazonaws.com. 5 NS ns-777.awsdns-33.net.
s3-w.us-east-2.amazonaws.com. 5 NS ns-1728.awsdns-24.co.uk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0