Apex domains cannot have CNAME records.
Question and response
Question
dig ispeg.de. NS
Answer
ispeg.de. 2 NS ns.nepustil.com.
ispeg.de. 2 NS ns1.ispeg.eu.
ispeg.de. 2 NS ns.LF.net.
Authority
The response has no authority records.
Additional
ns1.ispeg.eu. 2 A 178.132.64.130
ns.nepustil.com. 2 AAAA 2001:14f8:8:0:0:0:0:1
ns1.ispeg.eu. 2 AAAA 2a03:2380:2:4:0:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0