Apex domains cannot have CNAME records.
Question and response
Question
dig feeddex.nl. NS
Answer
feeddex.nl. 5 NS ns2.shockmedia.nl.
feeddex.nl. 5 NS ns1.shockmedia.nl.
feeddex.nl. 5 NS ns3.shockmedia.nl.
Authority
The response has no authority records.
Additional
ns1.shockmedia.nl. 5 A 31.7.0.53
ns2.shockmedia.nl. 5 A 45.63.42.250
ns3.shockmedia.nl. 5 A 3.74.8.24
ns1.shockmedia.nl. 5 AAAA 2a03:9700:0:0:0:0:0:53
ns2.shockmedia.nl. 5 AAAA 2001:19f0:5001:3169:5400:2ff:fe53:7a44
ns3.shockmedia.nl. 5 AAAA 2a05:d014:133d:1200:bfd:ccd2:7453:bd9b
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0