Apex domains cannot have CNAME records.
Question and response
Question
dig warman.nask.pl. NS
Answer
warman.nask.pl. 5 NS frodo.nask.waw.pl.
warman.nask.pl. 5 NS kirdan.nask.net.pl.
warman.nask.pl. 5 NS bilbo.nask.org.pl.
warman.nask.pl. 5 NS eomer.nask.net.pl.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0