app.luadns.com has no CNAME records.
Question and response
Question
dig app.luadns.com. NS
Answer
The response has no answer records.
Authority
luadns.com. 2129 SOA ns1.luadns.net. hostmaster.luadns.com. 1772610617 1200 120 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0