Mexican Casserole with Cornbread Topping

1 cup onion, chopped
1 green pepper, chopped
3 tablespoons dry taco seasoning mix**
1 (15-ounce) can chopped tomatoes
1 (15-ounce) can black beans, rinsed and drained
1 (15-ounce) can great northern beans, rinsed and drained
4 ounces Monterrey Jack cheese, shredded
1 package of cornbread mix, prepared as directed on box.

Saute pepper and onion in a large skillet over medium heat until crisp tender, about 5 minutes. Open can of tomatoes and discard 2 tablespoons of the liquid. Add taco seasoning mix (and salt if using), tomatoes with remaining liquid, and beans. Mix lightly. Let simmer about 5 minutes. If too watery, mix 1 tablespoon of corn starch with one tablespoon of water. Add to mixture and let bubble 1-2 minutes to thicken. Spoon mixture into 9x12-inch baking dish. Sprinkle with cheese. Pour prepared cornbread mix over the top. Spread to cover. Bake at 375ºF for 18-25 minutes or until cornbread is done.
Serves 4 to 6.

**Note-if using homemade taco seasoning, add about 1/2 teaspoon of salt along with the seasoning.
**Note-this can be made ahead and frozen, except for the cornbread mixture. Thaw completely in the fridge overnight and then cook as directed.