Apex domains cannot have CNAME records.
Question and response
Question
dig cave.kiev.ua. NS
Answer
cave.kiev.ua. 5 NS pola.ns.cloudflare.com.
cave.kiev.ua. 5 NS noah.ns.cloudflare.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0