Apex domains cannot have CNAME records.
Question and response
Question
dig knownhost.net. NS
Answer
knownhost.net. 4 NS ns1.knownhost.com.
knownhost.net. 4 NS ns2.knownhost.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0