Apex domains cannot have CNAME records.
Question and response
Question
dig enbw.com. NS
Answer
enbw.com. 5 NS nss02.enbw.com.
enbw.com. 5 NS nss03.enbw.com.
enbw.com. 5 NS nss04.enbw.com.
enbw.com. 5 NS nss01.enbw.com.
Authority
The response has no authority records.
Additional
nss01.enbw.com. 5 A 195.35.72.246
nss02.enbw.com. 5 A 195.35.72.247
nss03.enbw.com. 5 A 35.157.20.142
nss04.enbw.com. 5 A 63.177.21.180
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0