Apex domains cannot have CNAME records.
Question and response
Question
dig fischl.online. NS
Answer
fischl.online. 5 NS ns04.fischl.online.
fischl.online. 5 NS ns2.domaindiscount24.net.
fischl.online. 5 NS ns1.domaindiscount24.net.
fischl.online. 5 NS ns03.fischl.online.
fischl.online. 5 NS ns3.domaindiscount24.net.
Authority
The response has no authority records.
Additional
ns1.domaindiscount24.net. 5 A 193.227.117.34
ns2.domaindiscount24.net. 5 A 194.50.187.34
ns3.domaindiscount24.net. 5 A 194.0.182.34
ns03.fischl.online. 5 A 195.201.107.151
ns04.fischl.online. 5 A 78.46.56.170
ns1.domaindiscount24.net. 5 AAAA 2a04:2b00:14cc:0:0:0:0:34
ns2.domaindiscount24.net. 5 AAAA 2a04:2b00:14dd:0:0:0:0:34
ns3.domaindiscount24.net. 5 AAAA 2a04:2b00:14ee:0:0:0:0:34
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