Apex domains cannot have CNAME records.
Question and response
Question
dig ns2.nubehost.com.ar. NS
Answer
ns2.nubehost.com.ar. 5 NS ns1.179-60-232-60.cprapid.com.
ns2.nubehost.com.ar. 5 NS ns2.179-60-232-60.cprapid.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0