Apex domains cannot have CNAME records.
Question and response
Question
dig polonus-tel.com.pl. NS
Answer
polonus-tel.com.pl. 4 NS ns2.domena.pl.
polonus-tel.com.pl. 4 NS ns3.domena.pl.
polonus-tel.com.pl. 4 NS ns1.domena.pl.
Authority
The response has no authority records.
Additional
ns1.domena.pl. 4 A 193.239.44.33
ns2.domena.pl. 4 A 91.234.176.240
ns3.domena.pl. 4 A 195.110.49.49
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0