Apex domains cannot have CNAME records.
Question and response
Question
dig dreher.at. NS
Answer
dreher.at. 4 NS nsz.fueber.org.
dreher.at. 4 NS nsx.fueber.org.
Authority
The response has no authority records.
Additional
nsx.fueber.org. 4 A 167.233.1.169
nsz.fueber.org. 4 A 80.75.240.139
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0