Apex domains cannot have CNAME records.
Question and response
Question
dig us-gov-east-1.compute.amazonaws.com. NS
Answer
us-gov-east-1.compute.amazonaws.com. 4 NS ns-499.awsdns-62.com.
us-gov-east-1.compute.amazonaws.com. 4 NS ns-1168.awsdns-18.org.
us-gov-east-1.compute.amazonaws.com. 4 NS ns-547.awsdns-04.net.
us-gov-east-1.compute.amazonaws.com. 4 NS ns-1659.awsdns-15.co.uk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0