Apex domains cannot have CNAME records.
Question and response
Question
dig pbw.pl. NS
Answer
pbw.pl. 5 NS ns2.premium.pl.
pbw.pl. 5 NS ns1.premium.pl.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0