Apex domains cannot have CNAME records.
Question and response
Question
dig fischl-online.de. NS
Answer
fischl-online.de. 5 NS ns20.edevau.net.
fischl-online.de. 5 NS ns04.fischl.online.
fischl-online.de. 5 NS ns03.fischl.online.
fischl-online.de. 5 NS ns22.edevau.net.
Authority
The response has no authority records.
Additional
ns03.fischl.online. 5 A 195.201.107.151
ns04.fischl.online. 5 A 78.46.56.170
ns20.edevau.net. 5 A 217.64.80.5
ns22.edevau.net. 5 A 217.64.64.162
ns03.fischl.online. 5 AAAA 2a01:4f8:13a:3d7:0:0:0:3
ns04.fischl.online. 5 AAAA 2a01:4f8:201:2481:fa:0:0:402
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0