Apex domains cannot have CNAME records.
Question and response
Question
dig encoline.de. NS
Answer
encoline.de. 4 NS broceliande.iks-jena.de.
encoline.de. 4 NS avalon.iks-jena.de.
Authority
The response has no authority records.
Additional
avalon.iks-jena.de. 4 A 217.17.192.66
broceliande.iks-jena.de. 4 A 217.17.207.133
avalon.iks-jena.de. 4 AAAA 2001:4bd8:0:104:217:17:192:66
broceliande.iks-jena.de. 4 AAAA 2001:4bd8:52:1:20a:e4ff:fe80:bec8
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0