Apex domains cannot have CNAME records.
Question and response
Question
dig internetia.net.pl. NS
Answer
internetia.net.pl. 5 NS rumba.inetia.pl.
internetia.net.pl. 5 NS chacha.inetia.pl.
Authority
The response has no authority records.
Additional
rumba.inetia.pl. 5 A 195.114.181.130
chacha.inetia.pl. 5 A 195.114.161.2
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0