Apex domains cannot have CNAME records.
Question and response
Question
dig timmehosting.de. NS
Answer
timmehosting.de. 5 NS ns3.timmehosting.de.
timmehosting.de. 5 NS ns1.timmehosting.de.
timmehosting.de. 5 NS ns2.timmehosting.de.
Authority
The response has no authority records.
Additional
ns1.timmehosting.de. 5 A 78.47.168.192
ns2.timmehosting.de. 5 A 157.90.19.57
ns3.timmehosting.de. 5 A 94.237.31.204
ns1.timmehosting.de. 5 AAAA 2a01:4f8:c17:89e2:0:0:0:1
ns2.timmehosting.de. 5 AAAA 2a01:4f8:1c1e:b474:0:0:0:1
ns3.timmehosting.de. 5 AAAA 2a04:3542:1000:910:74b0:a6ff:feb3:4ad5
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0