Cut tortillas into triangles to avoid having to roll individual enchiladas.
In a casserole dish, place about half of the Beef and Peppers leftovers. (Draining the leftovers is recommend as the liquid can make the casserole soupy.) Top with one half of the corn tortillas and a light sprinkle of cheese (if desired). Repeat layers finishing with the tortillas.
In a food processor or blender, blend together canned tomatoes with garlic and cumin. Pour over the casserole and top with remaining cheese.
Cook in a 350 degree oven for 30 to 45 minutes or until the cheese has melted and the casserole is warm.
Serve with sour cream.