Apex domains cannot have CNAME records.
Question and response
Question
dig serviceprovider.nl. NS
Answer
serviceprovider.nl. 5 NS ns1.serviceprovider.nl.
serviceprovider.nl. 5 NS ns3.serviceprovider.nl.
serviceprovider.nl. 5 NS ns2.serviceprovider.nl.
serviceprovider.nl. 5 NS ns4.serviceprovider.nl.
Authority
The response has no authority records.
Additional
ns1.serviceprovider.nl. 5 A 185.104.28.19
ns2.serviceprovider.nl. 5 A 46.101.179.64
ns3.serviceprovider.nl. 5 A 178.62.208.8
ns4.serviceprovider.nl. 5 A 185.220.172.14
ns1.serviceprovider.nl. 5 AAAA 2a06:2ec0:1:0:0:0:0:10
ns2.serviceprovider.nl. 5 AAAA 2a03:b0c0:3:d0:0:0:116:2001
ns3.serviceprovider.nl. 5 AAAA 2a03:b0c0:2:d0:0:0:57:1001
ns4.serviceprovider.nl. 5 AAAA 2a06:2ec0:1:a:0:0:0:d53
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0