Apex domains cannot have CNAME records.
Question and response
Question
dig SIBDC.RU. NS
Answer
SIBDC.RU. 5 NS ns1.snt.RU.
SIBDC.RU. 5 NS ns2.snt.RU.
Authority
The response has no authority records.
Additional
ns1.snt.ru. 5 A 213.59.199.160
ns2.snt.ru. 5 A 188.128.82.232
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0