Apex domains cannot have CNAME records.
Question and response
Question
dig bmw.de. NS
Answer
bmw.de. 1 NS ns.bmw.de.
bmw.de. 1 NS ns4.m-online.net.
bmw.de. 1 NS ns3.m-online.net.
bmw.de. 1 NS ns2.m-online.net.
Authority
The response has no authority records.
Additional
ns.bmw.de. 1 A 192.109.190.2
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0