Apex domains cannot have CNAME records.
Question and response
Question
dig eu-west-2.compute.amazonaws.com. NS
Answer
eu-west-2.compute.amazonaws.com. 5 NS ns-642.awsdns-16.net.
eu-west-2.compute.amazonaws.com. 5 NS ns-1380.awsdns-44.org.
eu-west-2.compute.amazonaws.com. 5 NS ns-1981.awsdns-55.co.uk.
eu-west-2.compute.amazonaws.com. 5 NS ns-4.awsdns-00.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0