Heat oil in large skillet and saute onion until soft. Add beans, mashing with potato masher or back of wooden spoon. Add tomato juice which has been drained from diced tomatoes and chili powder. Continue cooking until beans are thickened and no liquid remains, about ten minutes. Stir in cheese and spoon mixture into taco shells. Serve two per person, and let each person top tacos with shredded lettuce, the diced tomatoes, sour cream and salsa, according to individual preference.

We love this, and eat it all the time. This quick, economical and low fat recipe will please even non-vegetarians.