Apex domains cannot have CNAME records.
Question and response
Question
dig ting-technology.de. NS
Answer
ting-technology.de. 5 NS ns4.stratoserver.net.
ting-technology.de. 5 NS ns3.stratoserver.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0