Preheat the oven to 375˚F. Line a 9x13-inch baking dish with Reynolds Wrap® Non-Stick Foil, dull (non-stick) side facing up. Set aside.

In a large skillet, heat oil over medium-high heat. Once the oil is shimmering, add onion and bell pepper. Cook for 6 to 7 minutes, until the vegetables are softened. Stir in garlic and cook for another 30 seconds to 1 minute until fragrant. Stir in chiles, beans, corn, chicken, 2 cups enchilada sauce, pumpkin puree, salt, and pepper. Once combined, remove from heat. Taste and season with additional salt and pepper to taste. Set aside.

Pour 1/2 cup remaining enchilada sauce into the bottom of the baking dish, spreading it to evenly coat the bottom of the dish. Top with a layer of tortilla halves (about 10 halves) so that the dish is covered. Top with 1/3 of the chicken mixture, then 1/3 of the cheeses. Repeat a layer of tortillas, chicken mixture, and cheese. Finish with a final layer of tortillas, chicken, remaining enchilada sauce, and cheese.

Cover the pan with Reynolds Wrap® Non-Stick Foil, making sure the dull, non-stick side is facing down. Bake for 20 minutes.

Remove from the oven, remove foil, and bake for 10 more minutes. The cheese should be melted completely and bubbling. Remove from the oven, garnish with desired toppings, and serve.