Apex domains cannot have CNAME records.
Question and response
Question
dig eu-west-2.elb.amazonaws.com. NS
Answer
eu-west-2.elb.amazonaws.com. 5 NS ns-654.awsdns-17.net.
eu-west-2.elb.amazonaws.com. 5 NS ns-1198.awsdns-21.org.
eu-west-2.elb.amazonaws.com. 5 NS ns-1934.awsdns-49.co.uk.
eu-west-2.elb.amazonaws.com. 5 NS ns-159.awsdns-19.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0