My MIL made this for us last week. It is quick, cheap and filling. I don't know the exact recipe she used, but I recreated it at home this way:
1 can black beans, drained and rinsed
1 jar salsa
1 can diced tomatoes
salt and pepper
sprinkle of cumin and/or chili powder
shredded cheese and/or sour cream (optional)
Heat all ingredients in a sauce pan until bubbling. Serve over polenta. Sprinkle with shredded cheese and/or sour cream if you like.