Apex domains cannot have CNAME records.
Question and response
Question
dig scaleway.email. NS
Answer
scaleway.email. 5 NS ns1.dom.scw.cloud.
scaleway.email. 5 NS ns0.dom.scw.cloud.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0