Apex domains cannot have CNAME records.
Question and response
Question
dig m-connect.de. NS
Answer
m-connect.de. 5 NS auth02.ns.td-fn.net.
m-connect.de. 5 NS auth01.ns.td-fn.net.
Authority
The response has no authority records.
Additional
auth01.ns.td-fn.net. 5 A 82.98.67.141
auth02.ns.td-fn.net. 5 A 217.24.194.130
auth01.ns.td-fn.net. 5 AAAA 2a02:2e0:401:7e1e:da7a:0:0:a
auth02.ns.td-fn.net. 5 AAAA 2a02:590:1:1:0:0:0:130
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0