Apex domains cannot have CNAME records.
Question and response
Question
dig neoserv.si. NS
Answer
neoserv.si. 1 NS ns3.avant.si.
neoserv.si. 1 NS ns0.avant.si.
neoserv.si. 1 NS ns1.avant.si.
neoserv.si. 1 NS ns4.avant.si.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0