Apex domains cannot have CNAME records.
Question and response
Question
dig codeplumbers.eu. NS
Answer
codeplumbers.eu. 3 NS ns1.online.net.
codeplumbers.eu. 3 NS ns0.online.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0