Apex domains cannot have CNAME records.
Question and response
Question
dig t-com.hr. NS
Answer
t-com.hr. 5 NS dns1.ht.hr.
t-com.hr. 5 NS dns2.ht.hr.
Authority
The response has no authority records.
Additional
dns1.ht.hr. 5 A 195.29.150.3
dns2.ht.hr. 5 A 195.29.247.220
dns1.ht.hr. 5 AAAA 2a00:c30:fffd:b:fe:b876:301e:6345
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0