Apex domains cannot have CNAME records.
Question and response
Question
dig nask.net.pl. NS
Answer
nask.net.pl. 2 NS bilbo.nask.pl.
nask.net.pl. 2 NS frodo.nask.net.pl.
nask.net.pl. 2 NS eomer.nask.pl.
nask.net.pl. 2 NS kirdan.nask.pl.
Authority
The response has no authority records.
Additional
bilbo.nask.pl. 2 A 195.187.245.51
eomer.nask.pl. 2 A 193.59.201.24
frodo.nask.net.pl. 2 A 193.59.201.37
kirdan.nask.pl. 2 A 195.187.244.8
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0