Apex domains cannot have CNAME records.
Question and response
Question
dig fcm.uncu.edu.ar. NS
Answer
fcm.uncu.edu.ar. 3 NS ns1.fcm.uncu.edu.ar.
Authority
The response has no authority records.
Additional
ns1.fcm.uncu.edu.ar. 3 A 200.12.137.14
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0