Apex domains cannot have CNAME records.
Question and response
Question
dig penza.com.ru. NS
Answer
penza.com.ru. 5 NS ns2.penza.com.ru.
penza.com.ru. 5 NS ns.penza.com.ru.
Authority
The response has no authority records.
Additional
ns.penza.com.ru. 5 A 81.200.240.18
ns2.penza.com.ru. 5 A 81.200.241.18
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0