Apex domains cannot have CNAME records.
Question and response
Question
dig kg.ac.RS. NS
Answer
kg.ac.rs. 4 NS ns1.unic.kg.ac.rs.
kg.ac.rs. 4 NS ns.rcub.bg.ac.rs.
kg.ac.rs. 4 NS ns1.uns.ac.rs.
kg.ac.rs. 4 NS ns.unic.kg.ac.rs.
kg.ac.rs. 4 NS ban.junis.ni.ac.rs.
Authority
The response has no authority records.
Additional
ns.rcub.bg.ac.rs. 4 A 147.91.1.5
ns.unic.kg.ac.rs. 4 A 147.91.209.2
ban.junis.ni.ac.rs. 4 A 160.99.1.1
ns1.uns.ac.rs. 4 A 147.91.173.4
ns1.unic.kg.ac.rs. 4 A 147.91.209.20
ns.rcub.bg.ac.rs. 4 AAAA 2001:4170:0:1:0:0:0:5
ns.unic.kg.ac.rs. 4 AAAA 2001:4170:3000:1:0:0:0:2
ban.junis.ni.ac.rs. 4 AAAA 2001:4170:2801:0:0:0:0:1
ns1.uns.ac.rs. 4 AAAA 2001:4170:2000:1:0:0:0:4
ns1.unic.kg.ac.rs. 4 AAAA 2001:4170:3000:1:0:0:0:20
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0