Preheat the oven to 350°F with a rack in the center of the oven.
Rub the skin of the sweet potatoes with the oil and season liberally with salt and pepper. Bake on a parchment lined baking sheet for 40-50 minutes until fork-tender. Allow to cool completely. Split each sweet potato in half lengthwise, and scoop out the fresh leaving a 1/4-inch border all the way around the sweet potato. Reserve the scooped out flesh for another meal.
Preheat the oven to 400°F. Place a baking rack on a rimmed baking sheet then arrange the potato skins skin side up on the rack. bake until the skins are lightly browned, 20-30 minutes. Let cool completely then cut each half in thirds.
Arrange the pieces skin side down on the rack then sprinkle with the walnut taco "meat", black beans, red onion and cheese. Bake until the cheese melts, 8-10 minutes. Remove from the oven and top with desired toppings to serve.