Apex domains cannot have CNAME records.
Question and response
Question
dig colo.iway.ch. NS
Answer
colo.iway.ch. 3 NS ns2.interway.ch.
colo.iway.ch. 3 NS ns1.interway.ch.
colo.iway.ch. 3 NS ns3.interway.ch.
Authority
The response has no authority records.
Additional
ns1.interway.ch. 3 A 194.246.118.119
ns2.interway.ch. 3 A 212.25.28.54
ns3.interway.ch. 3 A 72.14.185.13
ns1.interway.ch. 3 AAAA 2001:8e0:40:304:0:0:0:119
ns2.interway.ch. 3 AAAA 2001:8e0:80:0:0:0:0:54
ns3.interway.ch. 3 AAAA 2600:3c00:0:0:f03c:91ff:fe96:f81b
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0