Apex domains cannot have CNAME records.
Question and response
Question
dig a3bc.eu. NS
Answer
a3bc.eu. 5 NS ns2.a3bc.eu.
a3bc.eu. 5 NS ns1.a3bc.eu.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0