Apex domains cannot have CNAME records.
Question and response
Question
dig apple. NS
Answer
apple. 5 NS d.ns.apple.com.
apple. 5 NS c.ns.apple.com.
apple. 5 NS apple-ns.pch.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0