Cheesy Beef and Sweet Potato Taco Casserole

Preheat oven to 375 °F. Lightly spray a 9 x 13 baking dish with nonstick spray and set aside. Peel and spiralize sweet potatoes, chopping just a bit to shorten very long strands. If you don't have a spiralizer, just dice the sweet potato into small cubes. Set aside. In an extra-large skillet over medium to medium-high heat, brown beef with onion, breaking up any large chunks and stirring occasionally. When the pink color is almost gone from the beef, stir in garlic and cook for another 2 minutes. Stir in red pepper, corn, and sweet potato. Then add the beans, tomatoes, salsa, chili powder, cumin, paprika, oregano, cayenne pepper, salt, and black pepper, folding to combine. Turn heat down just a bit to medium and cook for about 15 minutes, stirring a few times. If you are using diced sweet potatoes rather than spiralized, you will need to cook this a bit longer. Just make sure that the sweet potato has softened. Spread 2 cups of the beef mixture into the bottom of the prepared baking dish. Layer tortilla chips on top, slightly overlapping the chips. Drop half of the remaining beef mixture by spoonfuls over the chips, and then spread it out into an even layer. Sprinkle half the Mexican cheese and half the pepper jack cheese over the beef mixture. Top with another layer of tortilla chips, followed by the remaining beef mixture and then the cheeses. Cover pan loosely with foil (so the foil doesn't touch the cheese) and cook for about 30 minutes, or until cheese is melted and the casserole is heated throughout. Remove foil, place pan under broiler, and broil until cheese is browned to your liking. Remove from oven and top with optional green onion and/or cilantro. Serve immediately with optional sour cream, guacamole, and/or salsa on the side.