Spray an 11×8-inch baking dish with cooking spray.
In a 12-inch stainless steel skillet, heat 3 tablespoons oil over medium heat. Add sweet potatoes; cook, stirring frequently, until just tender, 6 to 8 minutes. Transfer sweet potatoes to a medium bowl.
Heat remaining 1 tablespoon oil over medium heat. Add bell pepper, onion, and garlic; cook, stirring frequently, until softened, 3 to 4 minutes. Stir in tomato sauce, green chiles, taco seasoning, cilantro, and brown sugar; cook, stirring frequently, until heated through, 1 to 2 minutes. Reserve ½ cup sauce. Add sweet potatoes, beans, and corn to remaining sauce, stirring to combine.
Layer 6 tortillas in prepared dish, overlapping if necessary. Top with half of sweet potato mixture and ½ cup cheese. Repeat layers once; cover with remaining 6 tortillas. Spread reserved ½ cup sauce over top of sweet potato mixture, and sprinkle with remaining ½ cup cheese. Cover with foil. Bake as directed in Step 5.
Preheat oven to 350°. Bake for 25 minutes. Uncover and bake until bubbly, 5 to 10 minutes more. Let stand for 10 minutes before serving. Serve with sour cream and lime wedges. Garnish with cilantro, if desired.
Recipe by Taste of the South at https://tasteofthesouthmagazine.com/sweet-potato-enchilada-casserole/