Apex domains cannot have CNAME records.
Question and response
Question
dig dominiosbis.innovasur.com. NS
Answer
dominiosbis.innovasur.com. 2 NS dominios.innovasur.com.
dominiosbis.innovasur.com. 2 NS dominios.innovasur.es.
Authority
The response has no authority records.
Additional
dominios.innovasur.es. 4 A 46.39.192.80
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0