Apex domains cannot have CNAME records.
Question and response
Question
dig transtk.ru. NS
Answer
transtk.ru. 5 NS ns.transtelecom.net.
transtk.ru. 5 NS ns1.transtelecom.net.
transtk.ru. 5 NS dns-sec.transtk.ru.
transtk.ru. 5 NS dns-prim.transtk.ru.
Authority
The response has no authority records.
Additional
ns.transtelecom.net. 5 A 188.43.29.3
ns1.transtelecom.net. 5 A 188.43.30.219
dns-sec.transtk.ru. 5 A 217.150.32.19
dns-prim.transtk.ru. 5 A 217.150.32.18
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0