Soak Cashews: Place the cashews in a bowl and cover with just boiled water. If you have a high-speed blender like a Vitamix, you can soak for a minimum of 15 minutes. If you don't have a high-speed blender, soak for a minimum of 1 hour. After soaking, drain well.
When you're ready to proceed, preheat the oven to 425 F.
Make the Roasted Sweet Potatoes: Add the sweet potato cubes, chili powder, smoked paprika, garlic powder and cumin to a large baking sheet. Drizzle with the oil, season with a pinch of salt, then toss with your hands to coat and spread in a single layer. Roast on the middle rack for 20-25 minutes until tender.
Make the Slaw: Add the cabbage, lime juice, salt and a pinch of sugar to a mixing bowl and mix with your hands, massaging the cabbage to coat. Add the cilantro and toss to combine. Set aside.
Make the Queso: Add the soaked cashews and the rest of the queso ingredients to a high-powered blender. Process until smooth, stopping to scrape down the sides as needed. Taste and season with more salt or blend in a bit more water to adjust the consistency, if needed.
Cook the Onions: Heat 2 tsp oil over medium heat in a large skillet. Add the onions and a pinch of salt and pepper and cook for 3-5 minutes, stirring occasionally until softened.
Add the Spices: Add the garlic, chili powder and cumin and cook for 1 minute, stirring constantly, until fragrant.
Add the Black Beans and Water: Add the black beans and water and bring to a simmer. Once the mixture is simmering, reduce the heat to low and cook about 5-7 minutes, stirring often, until the liquid is reduced. Note: You can smash some of the beans with a potato masher, fork or back of a wooden spoon for a refried bean-like texture, adding more water as needed to reach your desired consistency. Warm Tortillas: If desired, warm tortillas over medium heat in a large pan or directly on a gas range.
Assemble Tacos: Place a scoop of the black bean mixture into a warm tortilla, top with sweet potatoes and a little slaw. Drizzle the queso over top. Add any other toppings you desire and enjoy. Repeat with remaining tortillas.