1) Heat the sauce ingredients in a medium pot over medium heat until simmering. Stir together to combine and simmer for 5-10 minutes until the sauce thickens slightly. Keep warm over low heat until needed.
2) Peel and chop the sweet potato (you want about a pound of sweet potato). Slice it into matchsticks and then chop it into 1 inch pieces.
3) In a large skillet, add a drizzle of oil over medium heat. Add chopped sweet potatoes and cook until they are browned lightly, about 6-8 minutes. Then add chopped onions and a pinch of salt and pepper and continue to cook until onions are soft.
4) Add salsa and drained and rinsed beans to the skillet and stir to combine and heat through. Once the mixture cooks for a few minutes, remove it from the heat and season it with salt and pepper.
5) TO make enchiladas, add a few spoonfuls of sauce to a large baking dish. Microwave flour tortillas for 20 seconds on high to loosen them. Then, working with one at a time, add some grated monterey jack cheese to the tortilla and top with sweet potato mixture.
Roll it tightly and place it in the baking dish. Repeat until you fill the baking dish. You should get 10-12 enchiladas in the dish and will probably have enough filling to do a smaller second dish.
6) Once your enchiladas are in the dish, pour sauce over the enchiladas. Top with crumbled queso fresco cheese.
7) Cover the dish with foil and bake it at 400 degrees for 10 minutes. Then remove the foil and broil it on high heat to crisp up the top of the enchiladas (3-5 minutes depending on your broiler). Keep a close eye on it while broiling as it can burn quickly.
8) Let enchiladas cool briefly and then serve with sour cream, avocado, and fresh cilantro.