Apex domains cannot have CNAME records.
Question and response
Question
dig zenbox.pl. NS
Answer
zenbox.pl. 2 NS ns1.zenbox.pl.
zenbox.pl. 2 NS ns2.zenbox.pl.
Authority
The response has no authority records.
Additional
ns1.zenbox.pl. 2 A 94.152.254.108
ns2.zenbox.pl. 2 A 94.152.255.108
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0