Apex domains cannot have CNAME records.
Question and response
Question
dig eu-south-2.compute.amazonaws.com. NS
Answer
eu-south-2.compute.amazonaws.com. 5 NS ns-788.awsdns-34.net.
eu-south-2.compute.amazonaws.com. 5 NS ns-1593.awsdns-07.co.uk.
eu-south-2.compute.amazonaws.com. 5 NS ns-12.awsdns-01.com.
eu-south-2.compute.amazonaws.com. 5 NS ns-1348.awsdns-40.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0