ns1.nette.pl has no CNAME records.
Question and response
Question
dig ns1.nette.pl. NS
Answer
The response has no answer records.
Authority
nette.pl. 6427 SOA ns2.nette.pl. info.nette.pl. 2025090201 86400 86400 2592000 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0