Apex domains cannot have CNAME records.
Question and response
Question
dig nask.pl. NS
Answer
nask.pl. 5 NS ns.tpnet.pl.
nask.pl. 5 NS bilbo.nask.pl.
nask.pl. 5 NS eomer.nask.pl.
nask.pl. 5 NS kirdan.nask.pl.
nask.pl. 5 NS nms.cyf-kr.edu.pl.
Authority
The response has no authority records.
Additional
nms.cyf-kr.edu.pl. 5 A 149.156.1.3
bilbo.nask.pl. 5 A 195.187.245.51
eomer.nask.pl. 5 A 193.59.201.24
kirdan.nask.pl. 5 A 195.187.244.8
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0