Apex domains cannot have CNAME records.
Question and response
Question
dig lhmail.eu. NS
Answer
lhmail.eu. 3 NS ns1.onlh.de.
lhmail.eu. 3 NS ns2.as213579.net.
Authority
The response has no authority records.
Additional
ns1.onlh.de. 3 A 185.140.54.7
ns1.onlh.de. 3 AAAA 2a14:47c0:e047:0:0:0:0:7
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0