Apex domains cannot have CNAME records.
Question and response
Question
dig fastwp.de. NS
Answer
fastwp.de. 3 NS ns1060.ui-dns.biz.
fastwp.de. 3 NS ns1016.ui-dns.de.
fastwp.de. 3 NS ns1027.ui-dns.com.
fastwp.de. 3 NS ns1033.ui-dns.org.
Authority
The response has no authority records.
Additional
ns1016.ui-dns.de. 1 A 217.160.80.16
ns1027.ui-dns.com. 1 A 217.160.82.27
ns1033.ui-dns.org. 1 A 217.160.83.33
ns1060.ui-dns.biz. 1 A 217.160.81.60
ns1016.ui-dns.de. 1 AAAA 2001:8d8:fe:53:0:d9a0:5010:100
ns1027.ui-dns.com. 1 AAAA 2001:8d8:fe:53:0:d9a0:521b:100
ns1033.ui-dns.org. 1 AAAA 2001:8d8:fe:53:0:d9a0:5321:100
ns1060.ui-dns.biz. 1 AAAA 2001:8d8:fe:53:0:d9a0:513c:100
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0