Apex domains cannot have CNAME records.
Question and response
Question
dig fioupfioup-infra.ch. NS
Answer
fioupfioup-infra.ch. 5 NS ns0.fioupfioup-infra.ch.
fioupfioup-infra.ch. 5 NS ns1.fioupfioup-infra.ch.
Authority
The response has no authority records.
Additional
ns0.fioupfioup-infra.ch. 5 A 37.35.106.20
ns1.fioupfioup-infra.ch. 5 A 57.129.4.234
ns1.fioupfioup-infra.ch. 5 AAAA 2001:41d0:701:1100:0:0:0:6ba9
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0