Apex domains cannot have CNAME records.
Question and response
Question
dig dsl-net.ch. NS
Answer
dsl-net.ch. 3 NS ns01.as1836.net.
dsl-net.ch. 3 NS ns01.agrinet.ch.
dsl-net.ch. 3 NS ns01.as1836.ch.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0