ruby.rubycom.com has no CNAME records.
Question and response
Question
dig ruby.rubycom.com. NS
Answer
The response has no answer records.
Authority
rubycom.com. 292 SOA ns1.dnsrubycom.com. equiposoporte.rubycom.com. 2025101101 3600 1800 1209600 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0