Apex domains cannot have CNAME records.
Question and response
Question
dig ap-northeast-3.compute.amazonaws.com. NS
Answer
ap-northeast-3.compute.amazonaws.com. 5 NS ns-1601.awsdns-08.co.uk.
ap-northeast-3.compute.amazonaws.com. 5 NS ns-726.awsdns-26.net.
ap-northeast-3.compute.amazonaws.com. 5 NS ns-509.awsdns-63.com.
ap-northeast-3.compute.amazonaws.com. 5 NS ns-1429.awsdns-50.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0