Apex domains cannot have CNAME records.
Question and response
Question
dig hightech-dent.com. NS
Answer
hightech-dent.com. 4 NS ns-412.awsdns-51.com.
hightech-dent.com. 4 NS ns-1013.awsdns-62.net.
hightech-dent.com. 4 NS ns-1331.awsdns-38.org.
hightech-dent.com. 4 NS ns-400.awsdns-50.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0