Chop roughly equal quantities celery, carrots and onion into smallish bits (1cm or so) -- probably somewhat less in total than your can of beans. Fry in butter or oil until they get a little more vibrant and start to smell good. Add cumin to taste, stir and fry a bit longer, then add to canned beans and heat/stir thoroughly. It's still on the simple side, but it'll add some nice flavour while letting the beans be themselves.