Brown meat & onion, add taco seasonings & stir in retried beans, mix soup & sour cream in separate bowl, spread 1/2 sourcream mixture on bottom of casserole dish, tear up 3 tortilla and spread over sourcream mixture. Put half the meat mixture over that,add layer of cheese, repeat layers, sprinkle cheese on top and bake uncovered at 350°f for 20-30 mins