Apex domains cannot have CNAME records.
Question and response
Question
dig SIBERIA.NET. NS
Answer
SIBERIA.NET. 3 NS b.ns.avantel.ru.
SIBERIA.NET. 3 NS a.ns.avantel.ru.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0