Apex domains cannot have CNAME records.
Question and response
Question
dig prima.net.ar. NS
Answer
prima.net.ar. 5 NS ns2.101domain.com.
prima.net.ar. 5 NS ns5.101domain.com.
prima.net.ar. 5 NS ns1.101domain.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0