Apex domains cannot have CNAME records.
Question and response
Question
dig fundaments.nl. NS
Answer
fundaments.nl. 5 NS clay.ns.cloudflare.com.
fundaments.nl. 5 NS linda.ns.cloudflare.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0