Apex domains cannot have CNAME records.
Question and response
Question
dig fbr.group. NS
Answer
fbr.group. 2 NS ns10.servicio-online.net.
fbr.group. 2 NS ns12.servicio-online.net.
fbr.group. 2 NS ns11.servicio-online.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0