Apex domains cannot have CNAME records.
Question and response
Question
dig pirxnet.pl. NS
Answer
pirxnet.pl. 3 NS dns.pirxnet.pl.
pirxnet.pl. 3 NS pirx.digi.pl.
pirxnet.pl. 3 NS max.digi.pl.
Authority
The response has no authority records.
Additional
max.digi.pl. 3 A 193.47.247.4
pirx.digi.pl. 3 A 188.123.209.209
dns.pirxnet.pl. 3 AAAA 2a02:2780:0:100:0:0:0:2
max.digi.pl. 3 AAAA 2a02:2780:0:100:0:0:0:4
pirx.digi.pl. 3 AAAA 2a02:2780:0:200:0:0:0:4
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0