Apex domains cannot have CNAME records.
Question and response
Question
dig tec.com. NS
Answer
tec.com. 5 NS meiling.ns.cloudflare.com.
tec.com. 5 NS hans.ns.cloudflare.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0