Apex domains cannot have CNAME records.
Question and response
Question
dig cbws.be. NS
Answer
cbws.be. 5 NS ns.cbws.be.
cbws.be. 5 NS ns.cbws.nl.
cbws.be. 5 NS ns.cbws.fr.
Authority
The response has no authority records.
Additional
ns.cbws.be. 5 A 185.142.141.163
ns.cbws.fr. 5 A 87.233.226.165
ns.cbws.nl. 5 A 185.142.141.148
ns.cbws.be. 5 AAAA 2a0b:b600:3803:0:0:0:0:53
ns.cbws.fr. 5 AAAA 2a0b:b600:3000:0:0:0:0:2
ns.cbws.nl. 5 AAAA 2a0b:b600:3802:0:0:0:0:53
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0