Apex domains cannot have CNAME records.
Question and response
Question
dig 240-28.65.16.194.in-addr.arpa. NS
Answer
240-28.65.16.194.in-addr.arpa. 5 NS ns.netset.se.
240-28.65.16.194.in-addr.arpa. 5 NS ns2.netset.se.
Authority
The response has no authority records.
Additional
ns.netset.se. 5 A 194.16.65.242
ns2.netset.se. 5 A 85.118.201.219
ns2.netset.se. 5 AAAA 2a06:6187:2:101:0:0:0:3
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0