For anyone else curious for the very basics of how to do this, here’s a curl example:
curl -X POST \
-H "Cookie: metabase.SESSION_ID=XXXXXXXXXXXXXXX" \
-H "Content-Type: application/json" \
-d '{"database":1"type":"query","query":{"source_table":2,"aggregation":["rows"],"breakout":[],"filter":[]}}' \
http://localhost:3000/api/dataset
(XXXXXXXXXXXXXXX is the value of a user’s session cookie. There’s also a X-METABASE-APIKEY header but I’m not sure if/how that works)
You can grab an existing query from your browser’s network panel or the server logs, or construct one using the query language.