Apex domains cannot have CNAME records.
Question and response
Question
dig kamensktel.ru. NS
Answer
kamensktel.ru. 5 NS ns2.kamensktel.ru.
kamensktel.ru. 5 NS ns3.kamensktel.ru.
kamensktel.ru. 5 NS ns1.kamensktel.ru.
Authority
The response has no authority records.
Additional
ns1.kamensktel.RU. 5 A 89.107.119.1
ns2.kamensktel.RU. 5 A 5.44.5.35
ns3.kamensktel.RU. 5 A 185.12.94.93
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0