Apex domains cannot have CNAME records.
Question and response
Question
dig tportal.hr. NS
Answer
tportal.hr. 5 NS dns2.t-com.hr.
tportal.hr. 5 NS dns1.t-com.hr.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0