aeson.vitkovice.cz has no CNAME records.
Question and response
Question
dig aeson.vitkovice.cz. NS
Answer
The response has no answer records.
Authority
vitkovice.cz. 300 SOA aeson.vitkovice.cz. hostmaster.vitkovice.cz. 2026012800 300 3600 172800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0