Apex domains cannot have CNAME records.
Question and response
Question
dig man.bydgoszcz.pl. NS
Answer
man.bydgoszcz.pl. 4 NS dns.man.bydgoszcz.pl.
man.bydgoszcz.pl. 4 NS sun1.utp.edu.pl.
Authority
The response has no authority records.
Additional
dns.man.bydgoszcz.pl. 4 A 212.122.200.3
sun1.utp.edu.pl. 5 A 212.122.192.34
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0