Cook the pasta according to the package instruction. Drain, and transfer to a mixing bowl. Preheat the oven to 350°F (175°C) and slightly grease a 10x6-inch baking dish with vegan butter or oil.
Prepare the sauce: add the pumpkin purée, almond milk, nutritional yeast, cornstarch, garlic, onion powder, salt, and ground black pepper to a saucepan. Whisk to dissolve the cornstarch.
Heat over medium heat, whisking constantly until it comes to a boil and starts to slightly thicken. Remove from heat and taste the sauce to adjust the saltiness to your liking (I ended up adding an extra 1/4 tsp of salt).
Pour the sauce over the cooked pasta. Add the kale, diced pumpkin, and stir to combine with the sauce. Transfer to the prepared baking dish. If using, sprinkle with vegan cheese.
Cover the dish with foil and bake for 40-45 minutes, or until the pumpkin cubes are tender. Remove from the oven and let cool a few minutes before serving. Top with chopped basil and serve hot!
This pumpkin pasta bake will keep for up to 3 days in the refrigerator. Reheat covered with foil for 10-15 minutes in a 350°F(175°C) preheated oven.