Apex domains cannot have CNAME records.
Question and response
Question
dig dinst.pl. NS
Answer
dinst.pl. 5 NS ns.dinst.pl.
dinst.pl. 5 NS ns0.pttk.pl.
Authority
The response has no authority records.
Additional
ns.dinst.pl. 5 A 178.19.105.67
ns0.pttk.pl. 5 A 213.77.35.126
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0