Apex domains cannot have CNAME records.
Question and response
Question
dig 3pc.de. NS
Answer
3pc.de. 5 NS ns1.3pc-dns.de.
3pc.de. 5 NS ns2.3pc-dns.de.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0