Apex domains cannot have CNAME records.
Question and response
Question
dig high5.nl. NS
Answer
high5.nl. 5 NS ns4.lowfive.nl.
high5.nl. 5 NS ns3.lowfive.nl.
high5.nl. 5 NS ns1.high5.nl.
high5.nl. 5 NS ns2.high5.nl.
Authority
The response has no authority records.
Additional
ns1.high5.nl. 5 A 46.23.80.23
ns2.high5.nl. 5 A 46.23.80.24
ns3.lowfive.nl. 5 A 45.76.37.64
ns4.lowfive.nl. 5 A 45.76.85.148
ns1.high5.nl. 5 AAAA 2a03:6000:800:0:0:0:0:23
ns2.high5.nl. 5 AAAA 2a03:6000:800:0:0:0:0:24
ns3.lowfive.nl. 5 AAAA 2a05:f480:1400:389:5400:3ff:fe9a:dac7
ns4.lowfive.nl. 5 AAAA 2a05:f480:1800:9:5400:3ff:fe9b:163
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0