Apex domains cannot have CNAME records.
Question and response
Question
dig mpcnet.pl. NS
Answer
mpcnet.pl. 5 NS dns2.home.pl.
mpcnet.pl. 5 NS dns3.home.pl.
mpcnet.pl. 5 NS dns.home.pl.
Authority
The response has no authority records.
Additional
dns.home.pl. 5 A 217.160.80.244
dns2.home.pl. 5 A 217.160.81.248
dns3.home.pl. 5 A 185.132.34.251
dns.home.pl. 5 AAAA 2001:8d8:fe:53:6870:0:0:1
dns2.home.pl. 5 AAAA 2001:8d8:fe:53:6870:0:0:2
dns3.home.pl. 5 AAAA 2607:f1c0:fe:53:185:132:34:251
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0