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