Apex domains cannot have CNAME records.
Question and response
Question
dig ap-south-2.compute.amazonaws.com. NS
Answer
ap-south-2.compute.amazonaws.com. 5 NS ns-1811.awsdns-34.co.uk.
ap-south-2.compute.amazonaws.com. 5 NS ns-282.awsdns-35.com.
ap-south-2.compute.amazonaws.com. 5 NS ns-932.awsdns-52.net.
ap-south-2.compute.amazonaws.com. 5 NS ns-1150.awsdns-15.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0