Apex domains cannot have CNAME records.
Question and response
Question
dig elm.net. NS
Answer
elm.net. 5 NS stitch.dns.badassops.com.
elm.net. 5 NS sin.at-the-beach.nl.
elm.net. 5 NS bar.at-the-beach.nl.
elm.net. 5 NS sun.at-the-beach.nl.
Authority
The response has no authority records.
Additional
bar.at-the-beach.nl. 5 A 188.34.184.97
sin.at-the-beach.nl. 5 A 198.99.80.108
sun.at-the-beach.nl. 5 A 81.172.129.161
stitch.dns.badassops.com. 5 A 208.111.35.197
bar.at-the-beach.nl. 5 AAAA 2a01:4f8:c012:7bd1:0:0:0:1
sin.at-the-beach.nl. 5 AAAA 2605:b40:1243:500:172:16:240:100
sun.at-the-beach.nl. 5 AAAA 2001:470:7a85:2f25:0:0:0:53
stitch.dns.badassops.com. 5 AAAA 2607:f740:0:3f:0:0:0:e49
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0