Chili Cheese Sweet Potato Casserole

Name: Chili Cheese Sweet Potato Casserole
Ingredients: 4 tbsp. neutral oil, divided, plus more for dish; 3 medium sweet potatoes (about 1 1/2 lb. total), peeled and cut into 1/2 cubes; 2 tsp. kosher salt, divided; 1 yellow onion, finely chopped; 1 red bell pepper, seeds and ribs removed, finely chopped; 2 cloves garlic, finely chopped; 1 tbsp. chili powder; 1 tbsp. ground cumin; 1 tsp. dried oregano; 1 (14.5-oz.) can black beans, drained and rinsed; 1 (14.5-oz.) can diced tomatoes; 1 (14.5-oz.) can tomato sauce; 1 c. fresh or frozen corn kernels; 2 c. shredded colby Jack cheese; 2 scallions, sliced (about 1/4 cup); Sour cream, for serving