Apex domains cannot have CNAME records.
Question and response
Question
dig us-east-1.elb.amazonaws.com. NS
Answer
us-east-1.elb.amazonaws.com. 5 NS ns-934.awsdns-52.net.
us-east-1.elb.amazonaws.com. 5 NS ns-235.awsdns-29.com.
us-east-1.elb.amazonaws.com. 5 NS ns-1793.awsdns-32.co.uk.
us-east-1.elb.amazonaws.com. 5 NS ns-1119.awsdns-11.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0