Apex domains cannot have CNAME records.
Question and response
Question
dig exoscale.net. NS
Answer
exoscale.net. 1 NS ns3.exoscale.net.
exoscale.net. 1 NS ns2.exoscale.net.
Authority
The response has no authority records.
Additional
ns2.exoscale.net. 1 A 185.19.31.244
ns3.exoscale.net. 1 A 185.19.31.243
ns2.exoscale.net. 1 AAAA 2a04:c43:f00:1:5054:ff:fe71:7ae
ns3.exoscale.net. 1 AAAA 2a04:c43:f00:1:5054:ff:fe92:1d99
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0