Apex domains cannot have CNAME records.
Question and response
Question
dig businessflex.by. NS
Answer
businessflex.by. 5 NS a2.domain.by.
businessflex.by. 5 NS a1.domain.by.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0