Apex domains cannot have CNAME records.
Question and response
Question
dig mrse.com.ar. NS
Answer
mrse.com.ar. 5 NS dns1.mrse.com.ar.
mrse.com.ar. 5 NS dns2.mrse.com.ar.
mrse.com.ar. 5 NS dns3.mrse.com.ar.
mrse.com.ar. 5 NS dns4.mrse.com.ar.
Authority
The response has no authority records.
Additional
dns1.mrse.com.ar. 5 A 200.51.254.216
dns2.mrse.com.ar. 5 A 200.51.254.207
dns3.mrse.com.ar. 5 A 200.51.254.249
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0