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