Apex domains cannot have CNAME records.
Question and response
Question
dig ilk.de. NS
Answer
ilk.de. 3 NS soa2.ilk.de.
ilk.de. 3 NS soa3.ilkdns.de.
ilk.de. 3 NS soa1.ilk.net.
Authority
The response has no authority records.
Additional
soa2.ilk.de. 3 A 194.45.22.72
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0