If you're using dried beans, sort through them first to remove dirt and bad ones, then rinse. Boil in water only until they're tender, but not even beginning to fall apart. Drain and cool.
Make the dressing by whisking all the dressing ingredients together and refrigerating. If you can make it an hour or more ahead of time, the flavors will blend well.
Toss all the vegetables except the tomato and the cilantro in a bowl. Pour the dressing over the top, add the tomato and cilantro, and toss again. This gets distinctly better if it sits about a half-hour before serving.
