Apex domains cannot have CNAME records.
Question and response
Question
dig bluewin.ch. NS
Answer
bluewin.ch. 5 NS ns33.scs-ns.net.
bluewin.ch. 5 NS ns32.scs-ns.org.
bluewin.ch. 5 NS ns31.scs-ns.ch.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0