Apex domains cannot have CNAME records.
Question and response
Question
dig dnstool.site. NS
Answer
dnstool.site. 1 NS betty.ns.cloudflare.com.
dnstool.site. 1 NS rocky.ns.cloudflare.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0