Apex domains cannot have CNAME records.
Question and response
Question
dig man.bialystok.pl. NS
Answer
man.bialystok.pl. 5 NS master.man.bialystok.pl.
man.bialystok.pl. 5 NS dns.man.bialystok.pl.
Authority
The response has no authority records.
Additional
master.man.bialystok.pl. 5 A 212.33.64.18
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0