Apex domains cannot have CNAME records.
Question and response
Question
dig cm.pc-net.ru. NS
Answer
cm.pc-net.ru. 4 NS ns2.pc-net.ru.
cm.pc-net.ru. 4 NS ns.pc-net.ru.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0