Apex domains cannot have CNAME records.
Question and response
Question
dig skynet.ru. NS
Answer
skynet.ru. 5 NS ns.sknt.ru.
skynet.ru. 5 NS skynet.ns.netexpert.ru.
Authority
The response has no authority records.
Additional
ns.SKNT.RU. 3 A 93.100.1.66
skynet.ns.netexpert.RU. 3 A 94.19.255.12
ns.SKNT.RU. 3 AAAA 2a05:3580:0:a1:0:0:0:0
skynet.ns.netexpert.RU. 3 AAAA 2a05:3580:0:a2:0:0:0:0
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0