Apex domains cannot have CNAME records.
Question and response
Question
dig snafu.de. NS
Answer
snafu.de. 5 NS ns01.snafu.de.
snafu.de. 5 NS ns02.snafu.de.
Authority
The response has no authority records.
Additional
ns01.snafu.de. 5 A 213.73.103.2
ns02.snafu.de. 5 A 78.46.25.196
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0