Apex domains cannot have CNAME records.
Question and response
Question
dig introlan.pl. NS
Answer
introlan.pl. 5 NS dns1.ih24.pl.
introlan.pl. 5 NS plato.ksiezyc.pl.
Authority
The response has no authority records.
Additional
plato.ksiezyc.pl. 5 A 46.45.78.1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0