Preheat the oven to 400°F.
Make the quick pickled cabbage: Add the cabbage and red onions to a medium bowl. In a separate small bowl, whisk together the salt, pepper, apple cider vinegar, and water. Once the salt is dissolved, pour the mixture over the cabbage and red onions. Stir to mix. Then, press the cabbage down so as to submerge as much of it as you can. As the cabbage sits, more liquid will accumulate and cover the cabbage. Cover the cabbage and set aside in the refrigerator for at least an hour.
Make the cashew sour cream: In an upright blender, combine the drained cashews, lemon juice, apple cider vinegar, salt, and water. Blend on high until you have a smooth and creamy consistency. Transfer cashew sour cream to a sealed container and store in the fridge until you’re ready to use it.
Make the sweet potato & pecan filling: Dice the peeled sweet potato into 1-inch cubes. Transfer the cubes to a baking sheet and toss with 2 teaspoons of the taco seasoning, the olive oil, some salt, and pepper. Slide the baking sheet into the oven and roast until sweet potatoes are browned and soft, about 35 minutes. Keep warm.
While sweet potatoes are roasting, make crumbled pecan “meat”: In a food processor, combine the pecan halves, remaining teaspoon of taco seasoning, tomato paste, coconut aminos, salt, and pepper. Pulse the food processor until you have a crumbly mixture that tastes good. Adjust for seasoning if necessary and set aside.
Make the cassava tortillas: In a medium bowl, whisk together the cassava flour, beet powder, salt, and baking soda. Add the olive oil and lemon juice, and whisk these into the dry mixture until you see little mealy bits. Then, add the water. Switch to stirring with a spatula. Stir the tortilla mixture until you have a unified, ever-so-slightly sticky textured tortilla dough. Divide the dough into 10 even balls and cover with a clean towel.
Heat a skillet or crepe pan over medium high heat. Using a tortilla press, flatten the balls to about 6-inches in diameter. Carefully transfer the pressed tortilla to your skillet and cook until lightly browned and dried out, about 30 seconds. Flip the tortilla to brown the other side for 30 seconds more.
Transfer the cooked tortilla to a plate and cover with a clean towel. Repeat cooking process with remaining balls of dough. Keep tortillas warm and covered.
Assemble the sweet potato pecan tacos!: In each tortilla spoon a bit of the pecan taco “meat.” Top that with some roasted sweet potato pieces. Garnish each taco with a tangle of the pickled cabbage, a drizzle of the cashew sour cream, and some chopped cilantro.