Apex domains cannot have CNAME records.
Question and response
Question
dig bialnet.pl. NS
Answer
bialnet.pl. 5 NS dns2.bialnet.pl.
bialnet.pl. 5 NS dns1.bialnet.pl.
Authority
The response has no authority records.
Additional
dns1.bialnet.pl. 5 A 91.239.155.200
dns2.bialnet.pl. 5 A 91.239.155.201
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0