Preheat the oven to 375 degrees and lightly grease a 9x9 baking dish.
Heat the olive oil in a large skillet over medium heat. Add the onion and cook until softened, about 3 minutes.
Stir in the garlic and cumin, then add the sweet potatoes. Cook for 8 to 10 minutes until the potatoes begin to soften. Season with salt and pepper.
Add the black beans to the skillet and stir to combine. Remove from heat.
Spread 1/2 cup enchilada sauce in the bottom of the baking dish. Layer 4 tortillas on top, followed by half the sweet potato mixture and 1/2 cup cheese.
Repeat the layers with the remaining tortillas, sweet potato mixture, another 1/2 cup sauce, and 1/2 cup cheese. Pour the remaining sauce over the top and finish with the last 1/2 cup cheese.
Bake for 25 to 30 minutes until the cheese is melted and the edges are bubbling. Let it rest for 5 minutes before cutting.