Apex domains cannot have CNAME records.
Question and response
Question
dig ap-northeast-1.compute.amazonaws.com. NS
Answer
ap-northeast-1.compute.amazonaws.com. 5 NS ns-137.awsdns-17.com.
ap-northeast-1.compute.amazonaws.com. 5 NS ns-900.awsdns-48.net.
ap-northeast-1.compute.amazonaws.com. 5 NS ns-1402.awsdns-47.org.
ap-northeast-1.compute.amazonaws.com. 5 NS ns-1886.awsdns-43.co.uk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0