Apex domains cannot have CNAME records.
Question and response
Question
dig t-2.si. NS
Answer
t-2.si. 5 NS dns1.t-2.si.
t-2.si. 5 NS dns2.t-2.si.
Authority
The response has no authority records.
Additional
dns1.t-2.si. 5 A 84.255.209.77
dns2.t-2.si. 5 A 84.255.210.77
dns1.t-2.si. 5 AAAA 2a01:260:1:2:0:0:0:4
dns2.t-2.si. 5 AAAA 2a01:260:1:3:0:0:0:4
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0