Apex domains cannot have CNAME records.
Question and response
Question
dig ugbb.net. NS
Answer
ugbb.net. 5 NS dns5.sbb.rs.
ugbb.net. 5 NS dns1.sbb.rs.
ugbb.net. 5 NS ns1.telemach.net.
ugbb.net. 5 NS ns2.telemach.net.
ugbb.net. 5 NS dns6.sbb.rs.
ugbb.net. 5 NS ns3.telemach.net.
ugbb.net. 5 NS dns2.sbb.rs.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0