Apex domains cannot have CNAME records.
Question and response
Question
dig EDGEDNS.RU. NS
Answer
EDGEDNS.RU. 5 NS ns2.edgedns.world.
EDGEDNS.RU. 5 NS ns1.edgedns.ru.
Authority
The response has no authority records.
Additional
ns1.EDGEDNS.RU. 5 A 5.188.176.176
ns1.EDGEDNS.RU. 5 AAAA 2a11:27c0:1010:0:0:0:0:1176
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0