Apex domains cannot have CNAME records.
Question and response
Question
dig server.wxp-1.nl. NS
Answer
server.wxp-1.nl. 5 NS ns2.wxp-1.nl.
server.wxp-1.nl. 5 NS ns1.wxp-1.nl.
Authority
The response has no authority records.
Additional
ns1.wxp-1.nl. 5 A 136.144.163.19
ns2.wxp-1.nl. 5 A 136.144.163.20
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0