Apex domains cannot have CNAME records.
Question and response
Question
dig com.ar. NS
Answer
com.ar. 4 NS f.dns.ar.
com.ar. 4 NS a.lactld.org.
com.ar. 4 NS d.dns.ar.
com.ar. 4 NS c.dns.ar.
com.ar. 4 NS e.dns.ar.
Authority
The response has no authority records.
Additional
c.dns.AR. 171185 A 200.108.148.50
d.dns.AR. 84005 A 192.140.126.50
e.dns.AR. 171195 A 170.238.66.50
f.dns.AR. 84005 A 130.59.31.20
c.dns.AR. 171185 AAAA 2801:140:10:0:0:0:0:10
d.dns.AR. 84005 AAAA 2801:140:dddd:0:0:0:0:50
e.dns.AR. 171195 AAAA 2801:140:eeee:0:0:0:0:50
f.dns.AR. 84005 AAAA 2001:620:0:ff:0:0:0:20
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0