Apex domains cannot have CNAME records.
Question and response
Question
dig cmd.com.ar. NS
Answer
cmd.com.ar. 4 NS ns-682.awsdns-21.net.
cmd.com.ar. 4 NS ns-4.awsdns-00.com.
cmd.com.ar. 4 NS ns-1951.awsdns-51.co.uk.
cmd.com.ar. 4 NS ns-1317.awsdns-36.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0