Make the pumpkin cashew cream: Blend together the cashews, water, lime juice, pumpkin sauce, garlic powder, and a pinch of salt and pepper. Taste and adjust seasonings. Chill until ready to serve.
Preheat the oven to 425°F and line a baking sheet with parchment paper. Slice the squash in half lengthwise, scoop out the seeds and slice into ½-inch segments. Toss the squash slices with a drizzle of olive oil and pinches of salt and pepper and roast until tender and golden brown, about 30 minutes.
Heat 1 tablespoon of olive oil in a medium skillet over medium heat. Add the onion slices and a pinch of salt and pepper and cook until soft and browned, 5 to 8 minutes, stirring occasionally. Add the mushrooms, and cook until they are soft and browned, about 5 more minutes, stirring occasionally. Add the apple cider vinegar, stir, reduce heat, and cook until the mushrooms are very soft. Stir in the kale and cook until it wilts, about 1 more minute. Season with salt and pepper to taste.
Assemble the tacos with the onion/mushroom/kale mixture and roasted squash. Top with desired toppings. Serve with the pumpkin cashew cream and lime slices.
Note: Soak the cashews in water 3 to 4 hours, preferably overnight, then drain and rinse.
