Put the sweet potato in a sauté pan with the chili powder, cumin, and salt. Cook, adding a bit of water or broth if it starts to stick, until it is soft -- about 8 to 10 minutes.
To make one quesadilla: Place a tortilla in a 10-inch warmed pan. Drizzle queso on the tortilla. To one half of the tortilla, add 1/6 of the sweet potato and 1/6 of the black beans.
Fold the other half of the tortilla over. Toast one side at a time.