Apex domains cannot have CNAME records.
Question and response
Question
dig ap-southeast-2.compute.amazonaws.com. NS
Answer
ap-southeast-2.compute.amazonaws.com. 5 NS ns-1761.awsdns-28.co.uk.
ap-southeast-2.compute.amazonaws.com. 5 NS ns-817.awsdns-38.net.
ap-southeast-2.compute.amazonaws.com. 5 NS ns-298.awsdns-37.com.
ap-southeast-2.compute.amazonaws.com. 5 NS ns-1201.awsdns-22.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0