Apex domains cannot have CNAME records.
Question and response
Question
dig sprint.pl. NS
Answer
sprint.pl. 5 NS raquel.ns.cloudflare.com.
sprint.pl. 5 NS rodrigo.ns.cloudflare.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0