Apex domains cannot have CNAME records.
Question and response
Question
dig keensystems.nl. NS
Answer
keensystems.nl. 5 NS auth1.keensystems.eu.
keensystems.nl. 5 NS auth3.keensystems.nl.
keensystems.nl. 5 NS auth2.keensystems.net.
Authority
The response has no authority records.
Additional
auth1.keensystems.eu. 5 A 185.42.9.20
auth2.keensystems.net. 5 A 185.42.11.20
auth3.keensystems.nl. 5 A 87.233.221.120
auth1.keensystems.eu. 5 AAAA 2a01:5860:2000:0:0:9:20:1
auth2.keensystems.net. 5 AAAA 2a01:5860:a000:0:0:11:20:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0