Preheat your oven to 350°F / 175°C.
In a large skillet, combine the chopped onions, undrained tomatoes, green pepper, picante sauce, cumin, and garlic.
Bring to a boil, then reduce the heat and simmer, uncovered, for 10 minutes.
Stir in the rinsed and drained beans.
To assemble, spread one-third of the bean mixture in the bottom of an ungreased 3-quart (9x13 inch) rectangular baking dish.
Top with 6 tortillas, overlapping as needed, and sprinkle with 1 cup (240 ml) of cheese.
Repeat the layers: Add another one-third of the bean mixture, top with the remaining 6 tortillas, and finish with the last of the bean mixture.
Cover the dish with foil and bake for 30 to 35 minutes, or until heated through. Carefully remove the foil and sprinkle with the remaining 1 cup (240 ml) of cheese.
Let the casserole stand for 10 minutes before slicing and serving. This helps it hold its shape.
Serve on shredded lettuce and garnish with fresh chile pepper, if desired.
