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. 4 NS ns-1199.awsdns-21.org.
s3-website-eu-west-1.amazonaws.com. 4 NS ns-873.awsdns-45.net.
s3-website-eu-west-1.amazonaws.com. 4 NS ns-414.awsdns-51.com.
s3-website-eu-west-1.amazonaws.com. 4 NS ns-1606.awsdns-08.co.uk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0