Apex domains cannot have CNAME records.
Question and response
Question
dig netherlands-3.vps.ac. NS
Answer
netherlands-3.vps.ac. 1 NS ns2.fotbo.host.
netherlands-3.vps.ac. 1 NS ns4.fotbo.org.
netherlands-3.vps.ac. 1 NS ns1.fotbo.com.
netherlands-3.vps.ac. 1 NS ns3.fotbo.cloud.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0