Apex domains cannot have CNAME records.
Question and response
Question
dig bar.at-the-beach.nl. NS
Answer
bar.at-the-beach.nl. 5 NS sun.at-the-beach.nl.
bar.at-the-beach.nl. 5 NS bar.at-the-beach.nl.
Authority
The response has no authority records.
Additional
bar.at-the-beach.nl. 4 A 188.34.184.97
sun.at-the-beach.nl. 4 A 81.172.129.161
bar.at-the-beach.nl. 4 AAAA 2a01:4f8:c012:7bd1:0:0:0:1
sun.at-the-beach.nl. 4 AAAA 2001:470:7a85:2f25:0:0:0:53
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0