Apex domains cannot have CNAME records.
Question and response
Question
dig efri.hr. NS
Answer
efri.hr. 5 NS oliver.efri.hr.
efri.hr. 5 NS bob.efri.hr.
efri.hr. 5 NS ns.ri.carnet.hr.
Authority
The response has no authority records.
Additional
bob.efri.hr. 5 A 161.53.42.4
oliver.efri.hr. 5 A 161.53.42.3
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0