Apex domains cannot have CNAME records.
Question and response
Question
dig dmax.de. NS
Answer
dmax.de. 5 NS ns-736.awsdns-28.net.
dmax.de. 5 NS ns-1234.awsdns-26.org.
dmax.de. 5 NS ns-1888.awsdns-44.co.uk.
dmax.de. 5 NS ns-471.awsdns-58.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0