Apex domains cannot have CNAME records.
Question and response
Question
dig digital.rt.ru. NS
Answer
digital.rt.ru. 5 NS ns2.digital.rt.ru.
digital.rt.ru. 5 NS ns4.digital.rt.ru.
digital.rt.ru. 5 NS ns1.digital.rt.ru.
digital.rt.ru. 5 NS ns3.digital.rt.ru.
Authority
The response has no authority records.
Additional
ns1.digital.rt.ru. 5 A 213.59.242.219
ns2.digital.rt.ru. 5 A 213.59.226.233
ns3.digital.rt.ru. 5 A 87.226.155.44
ns4.digital.rt.ru. 5 A 213.59.226.235
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0