Apex domains cannot have CNAME records.
Question and response
Question
dig ibercom.com. NS
Answer
ibercom.com. 5 NS ns10.servicio-online.net.
ibercom.com. 5 NS ns12.servicio-online.net.
ibercom.com. 5 NS ns11.servicio-online.net.
Authority
The response has no authority records.
Additional
ns10.servicio-online.net. 5 A 217.116.0.192
ns11.servicio-online.net. 5 A 217.116.0.149
ns12.servicio-online.net. 5 A 217.116.15.172
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0