Apex domains cannot have CNAME records.
Question and response
Question
dig hotelengine.eu. NS
Answer
hotelengine.eu. 5 NS c.ns.buddyns.com.
hotelengine.eu. 5 NS j.ns.buddyns.com.
hotelengine.eu. 5 NS k.ns.buddyns.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0