Apex domains cannot have CNAME records.
Question and response
Question
dig static.drei.at. NS
Answer
static.drei.at. 5 NS adns1.drei.com.
static.drei.at. 5 NS adns2.drei.at.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0