Apex domains cannot have CNAME records.
Question and response
Question
dig s1.dimastersoftware.ch. NS
Answer
s1.dimastersoftware.ch. 1 NS ns2.dimastersoftware.ch.
s1.dimastersoftware.ch. 1 NS ns1.dimastersoftware.ch.
Authority
The response has no authority records.
Additional
ns1.dimastersoftware.ch. 3 A 157.90.88.146
ns2.dimastersoftware.ch. 3 A 185.48.231.250
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0