Apex domains cannot have CNAME records.
Question and response
Question
dig edu. NS
Answer
edu. 5 NS c.edu-servers.net.
edu. 5 NS j.edu-servers.net.
edu. 5 NS k.edu-servers.net.
edu. 5 NS d.edu-servers.net.
edu. 5 NS b.edu-servers.net.
edu. 5 NS e.edu-servers.net.
edu. 5 NS i.edu-servers.net.
edu. 5 NS f.edu-servers.net.
edu. 5 NS g.edu-servers.net.
edu. 5 NS h.edu-servers.net.
edu. 5 NS m.edu-servers.net.
edu. 5 NS l.edu-servers.net.
edu. 5 NS a.edu-servers.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0