Apex domains cannot have CNAME records.
Question and response
Question
dig tntu.edu.ua. NS
Answer
tntu.edu.ua. 5 NS ns5.tntu.edu.ua.
tntu.edu.ua. 5 NS ns1.tntu.edu.ua.
tntu.edu.ua. 5 NS ns.tntu.edu.ua.
Authority
The response has no authority records.
Additional
ns.tntu.edu.ua. 5 A 91.198.10.1
ns1.tntu.edu.ua. 5 A 91.192.104.80
ns5.tntu.edu.ua. 5 A 91.198.10.4
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0