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