Apex domains cannot have CNAME records.
Question and response
Question
dig data443.io. NS
Answer
data443.io. 3 NS mack.ns.cloudflare.com.
data443.io. 3 NS irma.ns.cloudflare.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0