Apex domains cannot have CNAME records.
Question and response
Question
dig prorelay.nl. NS
Answer
prorelay.nl. 4 NS nsauth2.cyberfusion.nu.
prorelay.nl. 4 NS nsauth1.cyberfusion.nl.
prorelay.nl. 4 NS nsauth0.cyberfusion.nl.
Authority
The response has no authority records.
Additional
nsauth0.cyberfusion.nl. 4 A 185.233.173.153
nsauth1.cyberfusion.nl. 4 A 185.233.173.150
nsauth2.cyberfusion.nu. 4 A 91.195.80.142
nsauth0.cyberfusion.nl. 4 AAAA 2a0c:eb00:0:f10:185:233:173:153
nsauth1.cyberfusion.nl. 4 AAAA 2a0c:eb00:0:f10:185:233:173:150
nsauth2.cyberfusion.nu. 4 AAAA 2a00:1ca8:15:0:0:0:0:3c
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0