Apex domains cannot have CNAME records.
Question and response
Question
dig cv.ua. NS
Answer
cv.ua. 5 NS nix.ns.ua.
cv.ua. 5 NS ba1.ns.ua.
cv.ua. 5 NS ns.cv.ua.
Authority
The response has no authority records.
Additional
ns.cv.ua. 5 A 195.47.253.8
ns.cv.ua. 5 AAAA 2001:67c:258:0:0:0:0:8
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0