Apex domains cannot have CNAME records.
Question and response
Question
dig mts.com.ua. NS
Answer
mts.com.ua. 4 NS ns2.mts.com.ua.
mts.com.ua. 4 NS ns.mts.com.ua.
mts.com.ua. 4 NS ns.secondary.net.ua.
Authority
The response has no authority records.
Additional
ns.mts.com.ua. 4 A 80.255.64.67
ns2.mts.com.ua. 4 A 80.255.64.69
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0