Apex domains cannot have CNAME records.
Question and response
Question
dig telekom.RS. NS
Answer
telekom.RS. 5 NS ns1.telekom.RS.
telekom.RS. 5 NS ns1sl.telekom.RS.
Authority
The response has no authority records.
Additional
ns1.telekom.rs. 5 A 195.178.44.159
ns1sl.telekom.rs. 5 A 195.178.36.207
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0