Apex domains cannot have CNAME records.
Question and response
Question
dig deltatelesystems.ru. NS
Answer
deltatelesystems.ru. 4 NS ns1.deltatelesystems.ru.
deltatelesystems.ru. 4 NS ns2.deltatelesystems.ru.
Authority
The response has no authority records.
Additional
ns1.deltatelesystems.ru. 4 A 91.206.16.2
ns2.deltatelesystems.ru. 4 A 91.206.17.253
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0