Apex domains cannot have CNAME records.
Question and response
Question
dig marpemedical.com. NS
Answer
marpemedical.com. 5 NS ns-1575.awsdns-04.co.uk.
marpemedical.com. 5 NS ns-994.awsdns-60.net.
marpemedical.com. 5 NS ns-1562.awsdns-03.co.uk.
marpemedical.com. 5 NS ns-1649.awsdns-14.co.uk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0