Apex domains cannot have CNAME records.
Question and response
Question
dig ok.by. NS
Answer
ok.by. 4 NS ns2.ok.by.
ok.by. 4 NS ns3.ok.by.
ok.by. 4 NS ns1.ok.by.
Authority
The response has no authority records.
Additional
ns1.ok.by. 4 A 93.85.85.81
ns2.ok.by. 4 A 93.85.85.82
ns3.ok.by. 4 A 93.84.119.234
ns3.ok.by. 4 AAAA 2a02:2208:1:5:0:0:0:400
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0