Apex domains cannot have CNAME records.
Question and response
Question
dig meinberg.us. NS
Answer
meinberg.us. 5 NS ns2.meinberg.us.
meinberg.us. 5 NS ns1.meinberg.de.
meinberg.us. 5 NS ns3.meinberg.eu.
Authority
The response has no authority records.
Additional
ns1.meinberg.de. 5 A 49.12.79.151
ns2.meinberg.us. 5 A 78.47.60.48
ns3.meinberg.eu. 5 A 95.217.15.237
ns1.meinberg.de. 5 AAAA 2a01:4f8:c17:995d:0:0:0:1
ns2.meinberg.us. 5 AAAA 2a01:4f8:c0c:41e2:0:0:0:1
ns3.meinberg.eu. 5 AAAA 2a01:4f9:c010:5c9e:0:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0