Apex domains cannot have CNAME records.
Question and response
Question
dig 96-127.32.36.89.in-addr.arpa. NS
Answer
96-127.32.36.89.in-addr.arpa. 5 NS ns2.nuxoa.eu.
96-127.32.36.89.in-addr.arpa. 5 NS ns4.nuxoa.eu.
96-127.32.36.89.in-addr.arpa. 5 NS ns1.nuxoa.de.
96-127.32.36.89.in-addr.arpa. 5 NS ns3.nuxoa.de.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0