Apex domains cannot have CNAME records.
Question and response
Question
dig mariettakis.com. NS
Answer
mariettakis.com. 4 NS ns-646.awsdns-16.net.
mariettakis.com. 4 NS ns-1539.awsdns-00.co.uk.
mariettakis.com. 4 NS ns-392.awsdns-49.com.
mariettakis.com. 4 NS ns-1081.awsdns-07.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0