Apex domains cannot have CNAME records.
Question and response
Question
dig ELSSRV.ru. NS
Answer
ELSSRV.ru. 5 NS ns2.domenus.ru.
ELSSRV.ru. 5 NS ns1.domenus.ru.
Authority
The response has no authority records.
Additional
ns1.DOMENUS.RU. 5 A 77.87.208.8
ns2.domenus.ru. 5 A 31.28.20.107
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0