sec1.rcode0.com has no CNAME records.
Question and response
Question
dig sec1.rcode0.com. NS
Answer
The response has no answer records.
Authority
rcode0.com. 30 SOA sec1.rcode0.net. rcodezero.ipcom.at. 2026013104 10800 3600 604800 30
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0