Apex domains cannot have CNAME records.
Question and response
Question
dig host2.ledl.net. NS
Answer
host2.ledl.net. 5 NS ns4.domaintechnik.at.
host2.ledl.net. 5 NS ns3.domaintechnik.at.
host2.ledl.net. 5 NS ns1.domaintechnik.at.
host2.ledl.net. 5 NS ns2.domaintechnik.at.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0