Apex domains cannot have CNAME records.
Question and response
Question
dig mta2.hdems.com. NS
Answer
mta2.hdems.com. 5 NS ns-1809.awsdns-34.co.uk.
mta2.hdems.com. 5 NS ns-142.awsdns-17.com.
mta2.hdems.com. 5 NS ns-559.awsdns-05.net.
mta2.hdems.com. 5 NS ns-1153.awsdns-16.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0