Apex domains cannot have CNAME records.
Question and response
Question
dig polskiecentrum.org. NS
Answer
polskiecentrum.org. 5 NS ns-1114.awsdns-11.org.
polskiecentrum.org. 5 NS ns-546.awsdns-04.net.
polskiecentrum.org. 5 NS ns-1999.awsdns-57.co.uk.
polskiecentrum.org. 5 NS ns-1165.awsdns-17.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0