Apex domains cannot have CNAME records.
Question and response
Question
dig eunic.dn.ua. NS
Answer
eunic.dn.ua. 5 NS nss.dn.ua.
eunic.dn.ua. 5 NS nss.kh.ua.
eunic.dn.ua. 5 NS ns1.net.ua.
eunic.dn.ua. 5 NS nss.zp.ua.
eunic.dn.ua. 5 NS nss.sm.ua.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0