Apex domains cannot have CNAME records.
Question and response
Question
dig sm.ua. NS
Answer
sm.ua. 5 NS nn.ns.ua.
sm.ua. 5 NS ns.kh.ua.
sm.ua. 5 NS ns.dn.ua.
sm.ua. 5 NS ns.zp.ua.
sm.ua. 5 NS ns.net.ua.
sm.ua. 5 NS ho1.eunic.net.ua.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0