Apex domains cannot have CNAME records.
Question and response
Question
dig _spf.4web.pl. NS
Answer
_spf.4web.pl. 5 NS ns1.4web.pl.
_spf.4web.pl. 5 NS ns2.4web.pl.
Authority
The response has no authority records.
Additional
ns1.4web.pl. 5 A 194.63.133.2
ns2.4web.pl. 5 A 194.63.132.120
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0