Apex domains cannot have CNAME records.
Question and response
Question
dig mdrspcloud.de. NS
Answer
mdrspcloud.de. 4 NS ns3.nshost2.net.
mdrspcloud.de. 4 NS ns2.nshost2.de.
mdrspcloud.de. 4 NS ns1.nshost2.de.
Authority
The response has no authority records.
Additional
ns1.nshost2.de. 4 A 89.107.184.116
ns2.nshost2.de. 4 A 89.107.185.20
ns3.nshost2.net. 4 A 152.53.140.148
ns1.nshost2.de. 4 AAAA 2a01:50c0:1001:1:0:0:3:4
ns2.nshost2.de. 4 AAAA 2a01:50c0:1001:1:0:0:4:4
ns3.nshost2.net. 4 AAAA 2a0a:4cc0:c1:660:880a:29ff:feb2:ada5
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0