Apex domains cannot have CNAME records.
Question and response
Question
dig eu-west-1.amazonaws.com. NS
Answer
eu-west-1.amazonaws.com. 5 NS ns-1927.awsdns-48.co.uk.
eu-west-1.amazonaws.com. 5 NS ns-1189.awsdns-20.org.
eu-west-1.amazonaws.com. 5 NS ns-290.awsdns-36.com.
eu-west-1.amazonaws.com. 5 NS ns-549.awsdns-04.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0