Apex domains cannot have CNAME records.
Question and response
Question
dig es.sits.pro. NS
Answer
es.sits.pro. 5 NS ns2.sits.pro.
es.sits.pro. 5 NS ns1.sits.pro.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0