Apex domains cannot have CNAME records.
Question and response
Question
dig wittwer-it.ch. NS
Answer
wittwer-it.ch. 5 NS ns1.onlime.ch.
wittwer-it.ch. 5 NS ns3.onlime.ch.
wittwer-it.ch. 5 NS ns2.onlime.ch.
Authority
The response has no authority records.
Additional
ns1.onlime.ch. 5 A 46.231.201.200
ns2.onlime.ch. 5 A 78.46.160.129
ns3.onlime.ch. 5 A 46.231.201.213
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0