Apex domains cannot have CNAME records.
Question and response
Question
dig ap-south-1.amazonses.com. NS
Answer
ap-south-1.amazonses.com. 5 NS ns-631.awsdns-14.net.
ap-south-1.amazonses.com. 5 NS ns-1178.awsdns-19.org.
ap-south-1.amazonses.com. 5 NS ns-1944.awsdns-51.co.uk.
ap-south-1.amazonses.com. 5 NS ns-180.awsdns-22.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0