Apex domains cannot have CNAME records.
Question and response
Question
dig ap-southeast-3.compute.amazonaws.com. NS
Answer
ap-southeast-3.compute.amazonaws.com. 5 NS ns-1326.awsdns-37.org.
ap-southeast-3.compute.amazonaws.com. 5 NS ns-879.awsdns-45.net.
ap-southeast-3.compute.amazonaws.com. 5 NS ns-15.awsdns-01.com.
ap-southeast-3.compute.amazonaws.com. 5 NS ns-1665.awsdns-16.co.uk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0