Apex domains cannot have CNAME records.
Question and response
Question
dig agnat.pl. NS
Answer
agnat.pl. 5 NS ns1.agnat.pl.
agnat.pl. 5 NS ns3.agnat.pl.
agnat.pl. 5 NS ns2.agnat.pl.
Authority
The response has no authority records.
Additional
ns1.agnat.pl. 5 A 193.239.44.33
ns2.agnat.pl. 5 A 91.234.176.240
ns3.agnat.pl. 5 A 195.110.49.49
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0