Apex domains cannot have CNAME records.
Question and response
Question
dig santafe-conicet.gov.ar. NS
Answer
santafe-conicet.gov.ar. 5 NS ns2.santafe-conicet.gov.ar.
santafe-conicet.gov.ar. 5 NS ns1.santafe-conicet.gov.ar.
Authority
The response has no authority records.
Additional
ns1.santafe-conicet.gov.ar. 5 A 200.9.237.3
ns2.santafe-conicet.gov.ar. 5 A 200.9.237.7
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0