Apex domains cannot have CNAME records.
Question and response
Question
dig tu.kielce.pl. NS
Answer
tu.kielce.pl. 5 NS dns1.kielce.pl.
tu.kielce.pl. 5 NS dns.kielce.pl.
Authority
The response has no authority records.
Additional
dns.kielce.pl. 5 A 81.26.0.10
dns1.kielce.pl. 5 A 81.26.0.8
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0