Apex domains cannot have CNAME records.
Question and response
Question
dig rnids.rs. NS
Answer
rnids.rs. 5 NS nsu.dnsnode.net.
rnids.rs. 5 NS ns2.rnids.rs.
rnids.rs. 5 NS nordic1.dnsnode.net.
rnids.rs. 5 NS ns1.rnids.rs.
rnids.rs. 5 NS nsp.dnsnode.net.
rnids.rs. 5 NS odisej.telekom.rs.
Authority
The response has no authority records.
Additional
ns1.rnids.rs. 5 A 91.199.17.59
ns2.rnids.rs. 5 A 91.199.17.60
odisej.telekom.rs. 2 A 195.178.32.2
ns1.rnids.rs. 5 AAAA 2001:67c:69c:0:0:0:0:59
ns2.rnids.rs. 5 AAAA 2001:67c:69c:0:0:0:0:60
odisej.telekom.rs. 2 AAAA 2a00:e90:0:3:0:0:0:3
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0