Apex domains cannot have CNAME records.
Question and response
Question
dig sirena.siberia.net. NS
Answer
sirena.siberia.net. 5 NS ns.nvhost.ru.
sirena.siberia.net. 5 NS sirius.nvhost.ru.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0