Apex domains cannot have CNAME records.
Question and response
Question
dig lrz.de. NS
Answer
lrz.de. 5 NS dns3.lrz.eu.
lrz.de. 5 NS dns1.lrz.de.
lrz.de. 5 NS dns2.lrz.bayern.
Authority
The response has no authority records.
Additional
dns1.lrz.de. 5 A 129.187.19.183
dns1.lrz.de. 5 AAAA 2001:4ca0:0:100:0:53:1:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0