Apex domains cannot have CNAME records.
Question and response
Question
dig tensortelecom.ru. NS
Answer
tensortelecom.ru. 4 NS hdns.mts.ru.
tensortelecom.ru. 4 NS hdns2.mts.ru.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0