Apex domains cannot have CNAME records.
Question and response
Question
dig SVRV.RU. NS
Answer
SVRV.RU. 5 NS ns.masterhost.RU.
SVRV.RU. 5 NS ns1.masterhost.RU.
SVRV.RU. 5 NS ns2.masterhost.RU.
Authority
The response has no authority records.
Additional
ns.masterhost.RU. 4 A 90.156.136.116
ns1.masterhost.RU. 4 A 90.156.137.50
ns2.masterhost.RU. 4 A 90.156.133.161
ns.masterhost.RU. 4 AAAA 2a00:15f8:a000:10:1:1:0:53
ns1.masterhost.RU. 4 AAAA 2a00:15f8:a000:11:1:1:1:53
ns2.masterhost.RU. 4 AAAA 2a00:15f8:a000:12:1:1:2:53
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0