Apex domains cannot have CNAME records.
Question and response
Question
dig ap-southeast-4.compute.amazonaws.com. NS
Answer
ap-southeast-4.compute.amazonaws.com. 5 NS ns-897.awsdns-48.net.
ap-southeast-4.compute.amazonaws.com. 5 NS ns-363.awsdns-45.com.
ap-southeast-4.compute.amazonaws.com. 5 NS ns-1771.awsdns-29.co.uk.
ap-southeast-4.compute.amazonaws.com. 5 NS ns-1066.awsdns-05.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0