Apex domains cannot have CNAME records.
Question and response
Question
dig domain.by. NS
Answer
domain.by. 4 NS dns3.domain.by.
domain.by. 4 NS dns2.domain.by.
domain.by. 4 NS dns1.domain.by.
Authority
The response has no authority records.
Additional
dns1.domain.by. 4 A 93.85.85.81
dns2.domain.by. 4 A 93.85.85.82
dns3.domain.by. 4 A 93.84.119.234
dns3.domain.by. 4 AAAA 2a02:2208:1:5:0:0:0:400
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0