Preheat the oven to 375°F (190°C).

Peel and dice the sweet potatoes into small cubes. Place them in a large pot, cover with water, and boil for about 10-15 minutes until tender. Drain and mash the sweet potatoes in a mixing bowl.

In a large skillet, heat the olive oil over medium heat. Add the diced onion and sauté for about 5 minutes until translucent.

Add the minced garlic, cumin, and chili powder to the skillet, and cook for an additional minute.

Add the black beans, corn, and diced red bell pepper to the skillet. Stir to combine and cook for about 3-5 minutes. Season with salt and pepper to taste.

Combine the mashed sweet potatoes with the bean mixture, stirring until well mixed.

Spread a small amount of enchilada sauce on the bottom of a baking dish to prevent sticking.

Heat the corn tortillas briefly in a dry skillet or microwave until pliable. Fill each tortilla with the sweet potato mixture and roll them up tightly. Place them seam-side down in the baking dish.

Pour the remaining enchilada sauce over the top of the rolled tortillas. Bake in the preheated oven for 20-25 minutes, until heated through and bubbling.

Remove from the oven and let cool for a few minutes. Top with diced avocado and fresh cilantro before serving.