Apex domains cannot have CNAME records.
Question and response
Question
dig he-roes.de. NS
Answer
he-roes.de. 5 NS ns1031.ui-dns.com.
he-roes.de. 5 NS ns1031.ui-dns.org.
he-roes.de. 5 NS ns1037.ui-dns.biz.
he-roes.de. 5 NS ns1074.ui-dns.de.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0