Apex domains cannot have CNAME records.
Question and response
Question
dig km.ua. NS
Answer
km.ua. 5 NS nn.ns.ua.
km.ua. 5 NS ns.km.ua.
km.ua. 5 NS sx.ns.ua.
km.ua. 5 NS ba1.ns.ua.
km.ua. 5 NS ns2.km.ua.
km.ua. 5 NS ns3.km.ua.
Authority
The response has no authority records.
Additional
nn.ns.ua. 172487 A 194.58.197.4
nn.ns.ua. 172487 AAAA 2a01:3f1:c001:0:0:0:0:53
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0