Apex domains cannot have CNAME records.
Question and response
Question
dig exofilter.com. NS
Answer
exofilter.com. 5 NS ns3.exonet.eu.
exofilter.com. 5 NS ns1.exonet.nl.
exofilter.com. 5 NS ns2.exonet.nl.
Authority
The response has no authority records.
Additional
ns1.exonet.nl. 5 A 45.153.18.21
ns2.exonet.nl. 5 A 46.19.34.135
ns1.exonet.nl. 5 AAAA 2a00:1e29:4689:0:0:0:0:53
ns2.exonet.nl. 5 AAAA 2a02:2770:0:0:0:6494:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0