Apex domains cannot have CNAME records.
Question and response
Question
dig emailcenteruk.com. NS
Answer
emailcenteruk.com. 4 NS ns-36.awsdns-04.com.
emailcenteruk.com. 4 NS ns-1199.awsdns-21.org.
emailcenteruk.com. 4 NS ns-621.awsdns-13.net.
emailcenteruk.com. 4 NS ns-1811.awsdns-34.co.uk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0