Apex domains cannot have CNAME records.
Question and response
Question
dig 128-255.24.37.212.in-addr.arpa. NS
Answer
128-255.24.37.212.in-addr.arpa. 5 NS ns.wx3.se.
128-255.24.37.212.in-addr.arpa. 5 NS ns2.wx3.se.
Authority
The response has no authority records.
Additional
ns.wx3.se. 4 A 213.132.103.222
ns2.wx3.se. 4 A 213.132.103.218
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0