Apex domains cannot have CNAME records.
Question and response
Question
dig s3-fips-r-w.us-east-2.amazonaws.com. NS
Answer
s3-fips-r-w.us-east-2.amazonaws.com. 5 NS ns-1288.awsdns-33.org.
s3-fips-r-w.us-east-2.amazonaws.com. 5 NS ns-1586.awsdns-06.co.uk.
s3-fips-r-w.us-east-2.amazonaws.com. 5 NS ns-66.awsdns-08.com.
s3-fips-r-w.us-east-2.amazonaws.com. 5 NS ns-787.awsdns-34.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0