Apex domains cannot have CNAME records.
Question and response
Question
dig us-west-2.elb.amazonaws.com. NS
Answer
us-west-2.elb.amazonaws.com. 5 NS ns-560.awsdns-06.net.
us-west-2.elb.amazonaws.com. 5 NS ns-1475.awsdns-56.org.
us-west-2.elb.amazonaws.com. 5 NS ns-1769.awsdns-29.co.uk.
us-west-2.elb.amazonaws.com. 5 NS ns-332.awsdns-41.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0