Baja lasagna

1 pound ground round
1/4 cup chopped onion
2 (14 1/2 oz.) ready-cut tomatoes
3 oz. canned diced green chiles
1 cup sliced fresh mushrooms
2 2/3 cups drained, canned pinto beans
1 tablespoon chili powder
1 teaspoon cumin
8 corn tortillas, cut in 1 inch wide strips
2 cups shredded Cheddar cheese
1 cup sour cream
chopped fresh cilantro

Preheat oven to 350 degrees. Saute ground beef and onion until meat is not pink. Add tomatoes, chiles, mushrooms, beans, chili powder, and cumin. Simmer uncovered 10 minutes. In a baking dish, arrange a single layer of tortilla strips. Pour 1/4 of the tomato mixture and 1/3 of the cheese over the tortilla strips. Set aside a little of the cheese for garnishing. Repeat layers. Bake 30 minutes. For topping, spread layer of sour cream over casserole and sprinkle with chopped cilantro and reserved cheese.