Apex domains cannot have CNAME records.
Question and response
Question
dig corp.eurobyte.ru. NS
Answer
corp.eurobyte.ru. 5 NS dns1.eurobyte.ru.
Authority
The response has no authority records.
Additional
dns1.eurobyte.ru. 5 A 46.254.23.52
dns1.eurobyte.ru. 5 AAAA 2a03:c980:beef:6002:46:254:23:52
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0