f.tld.md has no CNAME records.
Question and response
Question
dig f.tld.md. NS
Answer
The response has no answer records.
Authority
tld.md. 3600 SOA ns.tld.md. master.tld.md. 2026022416 21600 3600 1209600 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0