Apex domains cannot have CNAME records.
Question and response
Question
dig undernet.org. NS
Answer
undernet.org. 5 NS alice.ns.cloudflare.com.
undernet.org. 5 NS gerald.ns.cloudflare.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0