Apex domains cannot have CNAME records.
Question and response
Question
dig usuarios.innovasur.com. NS
Answer
usuarios.innovasur.com. 4 NS dns02.innovasur.com.
usuarios.innovasur.com. 4 NS dns01.innovasur.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0