Apex domains cannot have CNAME records.
Question and response
Question
dig heliothermatics.com. NS
Answer
heliothermatics.com. 2 NS ns-1832.awsdns-37.co.uk.
heliothermatics.com. 2 NS ns-21.awsdns-02.com.
heliothermatics.com. 2 NS ns-796.awsdns-35.net.
heliothermatics.com. 2 NS ns-1260.awsdns-29.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0