Heat the oil in a medium or large skillet, add the onions, and cook over medium heat until soft and translucent, about 4 minutes.
Add the garlic, beans, tomato, and enough water just to cover.
Simmer until the beans are tender, then add the herbs and simmer 1 or 2 minutes more.
Season with salt and pepper to taste.
Serve hot, tepid, or even chilled.