Apex domains cannot have CNAME records.
Question and response
Question
dig agroweb.nl. NS
Answer
agroweb.nl. 2 NS ns1.agroweb.nl.
agroweb.nl. 2 NS ns2.agroweb.nl.
agroweb.nl. 2 NS ns3.agroweb.nl.
Authority
The response has no authority records.
Additional
ns1.agroweb.nl. 2 A 5.255.75.20
ns2.agroweb.nl. 2 A 5.255.75.21
ns3.agroweb.nl. 2 A 5.178.64.93
ns1.agroweb.nl. 2 AAAA 2a00:1ca8:1f:56:0:0:0:20
ns2.agroweb.nl. 2 AAAA 2a00:1ca8:1f:56:0:0:0:21
ns3.agroweb.nl. 2 AAAA 2a03:3f40:d:67:0:0:0:23
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0