Apex domains cannot have CNAME records.
Question and response
Question
dig s3-r-w.us-east-2.amazonaws.com. NS
Answer
s3-r-w.us-east-2.amazonaws.com. 5 NS ns-1009.awsdns-62.net.
s3-r-w.us-east-2.amazonaws.com. 5 NS ns-1428.awsdns-50.org.
s3-r-w.us-east-2.amazonaws.com. 5 NS ns-1974.awsdns-54.co.uk.
s3-r-w.us-east-2.amazonaws.com. 5 NS ns-90.awsdns-11.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0