Apex domains cannot have CNAME records.
Question and response
Question
dig jmdi.pl. NS
Answer
jmdi.pl. 5 NS ns2.jmdi.pl.
jmdi.pl. 5 NS ns1.jmdi.pl.
Authority
The response has no authority records.
Additional
ns1.jmdi.pl. 5 A 80.238.112.13
ns2.jmdi.pl. 5 A 80.238.112.12
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0