Apex domains cannot have CNAME records.
Question and response
Question
dig s3-fips-r-w.us-west-2.amazonaws.com. NS
Answer
s3-fips-r-w.us-west-2.amazonaws.com. 5 NS ns-153.awsdns-19.com.
s3-fips-r-w.us-west-2.amazonaws.com. 5 NS ns-890.awsdns-47.net.
s3-fips-r-w.us-west-2.amazonaws.com. 5 NS ns-1286.awsdns-32.org.
s3-fips-r-w.us-west-2.amazonaws.com. 5 NS ns-1774.awsdns-29.co.uk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0