Apex domains cannot have CNAME records.
Question and response
Question
dig outpost.vn.ua. NS
Answer
outpost.vn.ua. 5 NS ns1.outpost.vn.ua.
outpost.vn.ua. 5 NS ns2.nest.vn.ua.
outpost.vn.ua. 5 NS ns2.enet.vn.ua.
outpost.vn.ua. 5 NS ns4.nest.vn.ua.
Authority
The response has no authority records.
Additional
ns4.nest.vn.ua. 5 A 193.243.158.22
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0