Preheat oven to 450 degrees F. Peel and chop the sweet potato into 1/2-inch chunks. Add to a medium microwave-safe bowl with 3 tablespoons water. Cover with vented plastic and microwave 6 to 8 minutes, until very tender.

With a fork, mash sweet potato until mostly smooth. Fold in the black beans and chili powder. Season with salt and pepper to taste.

Line a large baking sheet with parchment and coat with cooking spray. Arrange 4 tortillas in a single layer on baking sheet. Spread sweet potato mixture onto tortillas. Top each with 1/2 cup cheese and remaining tortilla. Lightly coat tops of tortillas with cooking spray.

Bake 12 minutes, until tortillas are golden brown and crisp around edges, turning over once. Cut quesadillas into quarters. Serve with the salsa.