Apex domains cannot have CNAME records.
Question and response
Question
dig genericreverse.com. NS
Answer
genericreverse.com. 3 NS ns3.genericreverse.com.
genericreverse.com. 3 NS ns1.genericreverse.com.
Authority
The response has no authority records.
Additional
ns1.genericreverse.com. 3 A 204.74.208.2
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0