Apex domains cannot have CNAME records.
Question and response
Question
dig acul.me. NS
Answer
acul.me. 5 NS ns12.infomaniak.ch.
acul.me. 5 NS ns11.infomaniak.ch.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0