Apex domains cannot have CNAME records.
Question and response
Question
dig host.iwkd.pl. NS
Answer
host.iwkd.pl. 5 NS merkury.perfect.net.pl.
host.iwkd.pl. 5 NS serwer.inglobus.pl.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0