Apex domains cannot have CNAME records.
Question and response
Question
dig CORBINA.RU. NS
Answer
CORBINA.RU. 1 NS dns1.corbina.ru.
CORBINA.RU. 1 NS dns2.corbina.ru.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0