Apex domains cannot have CNAME records.
Question and response
Question
dig de. NS
Answer
de. 5 NS n.de.net.
de. 5 NS z.nic.de.
de. 5 NS f.nic.de.
de. 5 NS a.nic.de.
de. 5 NS l.de.net.
de. 5 NS s.de.net.
Authority
The response has no authority records.
Additional
a.nic.de. 71779 A 194.0.0.53
f.nic.de. 72382 A 81.91.164.5
z.nic.de. 72382 A 194.246.96.1
a.nic.de. 71779 AAAA 2001:678:2:0:0:0:0:53
f.nic.de. 72382 AAAA 2a02:568:0:2:0:0:0:53
z.nic.de. 72382 AAAA 2a02:568:fe02:0:0:0:0:de
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0