Apex domains cannot have CNAME records.
Question and response
Question
dig tmag.de. NS
Answer
tmag.de. 5 NS ns2.nsserve.de.
tmag.de. 5 NS ns1.nsserve.de.
tmag.de. 5 NS ns1.namesserver.net.
tmag.de. 5 NS ns2.namesserver.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0