Apex domains cannot have CNAME records.
Question and response
Question
dig techbriefs.com. NS
Answer
techbriefs.com. 4 NS ns-1292.awsdns-33.org.
techbriefs.com. 4 NS ns-2005.awsdns-58.co.uk.
techbriefs.com. 4 NS ns-19.awsdns-02.com.
techbriefs.com. 4 NS ns-702.awsdns-23.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0