Apex domains cannot have CNAME records.
Question and response
Question
dig muenchenticket.de. NS
Answer
muenchenticket.de. 1 NS ns2.webport.de.
muenchenticket.de. 1 NS ns1.webport.de.
Authority
The response has no authority records.
Additional
ns1.webport.de. 1 A 88.217.208.5
ns2.webport.de. 1 A 37.200.98.216
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0