Apex domains cannot have CNAME records.
Question and response
Question
dig artheroin.com. NS
Answer
artheroin.com. 5 NS ns-1956.awsdns-52.co.uk.
artheroin.com. 5 NS ns-380.awsdns-47.com.
artheroin.com. 5 NS ns-484.awsdns-60.com.
artheroin.com. 5 NS ns-1237.awsdns-26.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0