Apex domains cannot have CNAME records.
Question and response
Question
dig ewoffice.ch. NS
Answer
ewoffice.ch. 2 NS dns1.ewdns.ch.
ewoffice.ch. 2 NS dns3.ewdns.ch.
ewoffice.ch. 2 NS dns2.ewdns.ch.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0