Preheat oven to 350.
Peel and chop the sweet potatoes, then boil until tender (15-18 minutes).
In a large bowl, combine the beans, Rotel, corn, scallions (white parts only) and taco sauce, mixing well.
When the sweet potatoes are cooked, mash them then add the lime juice, sea salt, pepper, and chili powder, and set aside.
Drizzle bottom of 9x13 casserole or baking dish with 2-3 tablespoons of taco sauce, making sure the entire bottom is covered. Arrange tortilla halves across bottom of pan.
Cover tortillas with half of the sweet potato mixture, gently spreading to get maximum coverage. Next add a layer of the bean/corn mix (half of what you have), followed by a layer of tortillas.
Repeat once, ending with a layer of tortillas on top (this makes 3 layers of tortillas, total). Cover with salsa, cheese and the rest of your sliced scallions.
Cover with foil and bake for 20 minutes, remove foil and bake for another 5-8 until cheese is fully melted.