Apex domains cannot have CNAME records.
Question and response
Question
dig p01.hosting.k.pl. NS
Answer
p01.hosting.k.pl. 5 NS ns2.hosting.k.pl.
p01.hosting.k.pl. 5 NS ns1.hosting.k.pl.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0