Apex domains cannot have CNAME records.
Question and response
Question
dig adslplus.ch. NS
Answer
adslplus.ch. 5 NS ns4.sunrise.ch.
adslplus.ch. 5 NS ns2.sunrise.ch.
adslplus.ch. 5 NS ns1.sunrise.ch.
adslplus.ch. 5 NS ns3.sunrise.ch.
Authority
The response has no authority records.
Additional
ns1.sunrise.ch. 5 A 212.98.37.132
ns2.sunrise.ch. 5 A 194.230.55.100
ns3.sunrise.ch. 5 A 212.98.37.132
ns4.sunrise.ch. 5 A 194.230.55.100
ns1.sunrise.ch. 5 AAAA 2001:1700:a00:0:0:0:0:2
ns2.sunrise.ch. 5 AAAA 2001:1700:a00:0:0:0:0:3
ns3.sunrise.ch. 5 AAAA 2001:1700:a00:0:0:0:0:2
ns4.sunrise.ch. 5 AAAA 2001:1700:a00:0:0:0:0:3
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0