Apex domains cannot have CNAME records.
Question and response
Question
dig mailtempresas.com.ar. NS
Answer
mailtempresas.com.ar. 4 NS dns2.advance.com.ar.
mailtempresas.com.ar. 4 NS dns1.advance.com.ar.
Authority
The response has no authority records.
Additional
dns1.advance.com.ar. 4 A 209.13.119.20
dns2.advance.com.ar. 4 A 209.13.119.21
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0