Apex domains cannot have CNAME records.
Question and response
Question
dig dts.net.ua. NS
Answer
dts.net.ua. 5 NS ns.trifle.net.
dts.net.ua. 5 NS ns.dts.net.ua.
dts.net.ua. 5 NS ns2.dts.net.ua.
Authority
The response has no authority records.
Additional
ns.dts.net.ua. 5 A 91.203.63.1
ns.trifle.net. 2 A 195.24.156.222
ns.trifle.net. 2 AAAA 2a01:750:1:222:0:0:0:2
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0