Apex domains cannot have CNAME records.
Question and response
Question
dig netium.pl. NS
Answer
netium.pl. 5 NS ns1.netium.pl.
netium.pl. 5 NS ns2.netium.pl.
Authority
The response has no authority records.
Additional
ns1.netium.pl. 5 A 185.73.211.3
ns2.netium.pl. 5 A 193.138.118.6
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0