Apex domains cannot have CNAME records.
Question and response
Question
dig s3-website-us-west-1.amazonaws.com. NS
Answer
s3-website-us-west-1.amazonaws.com. 5 NS ns-1362.awsdns-42.org.
s3-website-us-west-1.amazonaws.com. 5 NS ns-1604.awsdns-08.co.uk.
s3-website-us-west-1.amazonaws.com. 5 NS ns-414.awsdns-51.com.
s3-website-us-west-1.amazonaws.com. 5 NS ns-687.awsdns-21.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0