Apex domains cannot have CNAME records.
Question and response
Question
dig ns5.be. NS
Answer
ns5.be. 5 NS ns0.nl.
ns5.be. 5 NS ns5.be.
ns5.be. 5 NS ns11.net.
Authority
The response has no authority records.
Additional
ns0.nl. 5 A 195.135.195.95
ns5.be. 5 A 195.8.195.95
ns11.net. 5 A 37.97.199.95
ns0.nl. 5 AAAA 2a01:7c8:dddd:195:0:0:0:95
ns5.be. 5 AAAA 2a01:7c8:7000:195:0:0:0:95
ns11.net. 5 AAAA 2a01:7c8:f:c1f:0:0:0:95
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0