Apex domains cannot have CNAME records.
Question and response
Question
dig umd.edu. NS
Answer
umd.edu. 5 NS ns1.umd.edu.
umd.edu. 5 NS ns.ums.edu.
umd.edu. 5 NS ns2.umd.edu.
Authority
The response has no authority records.
Additional
ns1.umd.edu. 5 A 128.8.74.3
ns2.umd.edu. 5 A 128.8.76.3
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0