Apex domains cannot have CNAME records.
Question and response
Question
dig opbverse.de.com. NS
Answer
opbverse.de.com. 5 NS carl.ns.cloudflare.com.
opbverse.de.com. 5 NS ulla.ns.cloudflare.com.
Authority
The response has no authority records.
Additional
carl.ns.cloudflare.com. 5 A 108.162.193.106
carl.ns.cloudflare.com. 5 A 172.64.33.106
carl.ns.cloudflare.com. 5 A 173.245.59.106
ulla.ns.cloudflare.com. 5 A 108.162.192.233
ulla.ns.cloudflare.com. 5 A 172.64.32.233
ulla.ns.cloudflare.com. 5 A 173.245.58.233
carl.ns.cloudflare.com. 5 AAAA 2606:4700:58:0:0:0:adf5:3b6a
carl.ns.cloudflare.com. 5 AAAA 2803:f800:50:0:0:0:6ca2:c16a
carl.ns.cloudflare.com. 5 AAAA 2a06:98c1:50:0:0:0:ac40:216a
ulla.ns.cloudflare.com. 5 AAAA 2606:4700:50:0:0:0:adf5:3ae9
ulla.ns.cloudflare.com. 5 AAAA 2803:f800:50:0:0:0:6ca2:c0e9
ulla.ns.cloudflare.com. 5 AAAA 2a06:98c1:50:0:0:0:ac40:20e9
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0