Apex domains cannot have CNAME records.
Question and response
Question
dig icep.avmail.ru. NS
Answer
icep.avmail.ru. 5 NS dnsproxy2.fm.nic.ru.
icep.avmail.ru. 5 NS dnsproxy1.fm.nic.ru.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0