Apex domains cannot have CNAME records.
Question and response
Question
dig extrim.ru. NS
Answer
extrim.ru. 4 NS ns0.mirasystem.net.
extrim.ru. 4 NS ns1.mirasystem.net.
Authority
The response has no authority records.
Additional
ns0.mirasystem.net. 4 A 212.49.118.3
ns1.mirasystem.net. 4 A 212.49.103.3
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0