Apex domains cannot have CNAME records.
Question and response
Question
dig wallner.digital. NS
Answer
wallner.digital. 1 NS oxygen.ns.hetzner.com.
wallner.digital. 1 NS helium.ns.hetzner.de.
wallner.digital. 1 NS hydrogen.ns.hetzner.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0