Apex domains cannot have CNAME records.
Question and response
Question
dig exoscale.ch. NS
Answer
exoscale.ch. 2 NS serena.ns.cloudflare.com.
exoscale.ch. 2 NS buck.ns.cloudflare.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0