Apex domains cannot have CNAME records.
Question and response
Question
dig IMT.SU. NS
Answer
IMT.SU. 2 NS ns2.imt.ru.
IMT.SU. 2 NS ns1.imt.ru.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0