Apex domains cannot have CNAME records.
Question and response
Question
dig ryt.itu.uncu.edu.ar. NS
Answer
ryt.itu.uncu.edu.ar. 5 NS noc.uncu.edu.ar.
ryt.itu.uncu.edu.ar. 5 NS ryt-itu.ryt.itu.uncu.edu.ar.
ryt.itu.uncu.edu.ar. 5 NS impsat.itu.uncu.edu.ar.
Authority
The response has no authority records.
Additional
noc.uncu.edu.ar. 1 A 170.210.2.97
ryt-itu.ryt.itu.uncu.edu.ar. 5 A 200.12.135.18
noc.uncu.edu.ar. 1 AAAA 2800:110:2800:296:21a:4aff:fe77:7122
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0