Preheat oven to 400 degrees F.
Place beans, tomatoes and the corn, salsa, bell pepper, garlic, and cumin in a saucepan. Stir and bring to a boil over medium-high heat, then reduce the heat to medium-low and let simmer, uncovered, until thickened, 4 to 5 minutes.
Spoon a third of the bean mixture over the bottom of a 13x9 inch baking dish. Top it with 5 of the tortillas, overlapping them as needed. Scatter 1 cup of the cheese over the tortillas. Spoon half of the remaining bean mixture over the cheese and top it with the remaining tortilaas. Spoon the remaining bean mixture over the tortillas, spreading it out to completely cover them. Cover the baking dish with foil.
Bake for 15 minutes, then remove from oven and uncover. Sprinkle remaining 1 cup cheese on top and return to oven. Bake until the cheese melts, 7 to 8 minutes. Let the casserole rest 1o minutes before slicing and serving.