In a large bowl, combine the beans, potato, cucumber, and onion.

To make the dressing, combine all the ingredients in a small bowl. Taste and adjust the seasonings as needed. Add the dressing to the veggies and mix until thoroughly combined. Serve topped with cilantro.

Substitute just about any cooked beans that you have in the fridge, though kidneys and chickpeas tend to keep their shape the best. Add shredded or chopped carrots, summer squash, or even a few spicy radish slices to make it a dish all your own.