Apex domains cannot have CNAME records.
Question and response
Question
dig s3-website.eu-west-1.amazonaws.com. NS
Answer
s3-website.eu-west-1.amazonaws.com. 5 NS ns-736.awsdns-28.net.
s3-website.eu-west-1.amazonaws.com. 5 NS ns-379.awsdns-47.com.
s3-website.eu-west-1.amazonaws.com. 5 NS ns-1990.awsdns-56.co.uk.
s3-website.eu-west-1.amazonaws.com. 5 NS ns-1078.awsdns-06.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0