Apex domains cannot have CNAME records.
Question and response
Question
dig multimetro.pl. NS
Answer
multimetro.pl. 5 NS dns.miconet.pl.
multimetro.pl. 5 NS dns1.miconet.pl.
Authority
The response has no authority records.
Additional
dns.miconet.pl. 5 A 195.225.36.2
dns1.miconet.pl. 5 A 195.225.36.16
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0