Apex domains cannot have CNAME records.
Question and response
Question
dig dmopp.de. NS
Answer
dmopp.de. 5 NS ns1034.ui-dns.de.
dmopp.de. 5 NS ns1016.ui-dns.org.
dmopp.de. 5 NS ns1110.ui-dns.biz.
dmopp.de. 5 NS ns1064.ui-dns.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0