Apex domains cannot have CNAME records.
Question and response
Question
dig admin.net.pl. NS
Answer
admin.net.pl. 5 NS ns1.admin.net.pl.
admin.net.pl. 5 NS ns3.admin.net.pl.
admin.net.pl. 5 NS ns2.admin.net.pl.
Authority
The response has no authority records.
Additional
ns1.admin.net.pl. 5 A 46.248.186.94
ns2.admin.net.pl. 5 A 212.91.26.139
ns3.admin.net.pl. 5 A 80.72.35.162
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0