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