Apex domains cannot have CNAME records.
Question and response
Question
dig eu-west-3.compute.amazonaws.com. NS
Answer
eu-west-3.compute.amazonaws.com. 5 NS ns-1006.awsdns-61.net.
eu-west-3.compute.amazonaws.com. 5 NS ns-1253.awsdns-28.org.
eu-west-3.compute.amazonaws.com. 5 NS ns-1887.awsdns-43.co.uk.
eu-west-3.compute.amazonaws.com. 5 NS ns-181.awsdns-22.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0