Bring a medium pot of salted water to a boil. Add the pasta. Cook the pasta according to pasta maker's instructions, or until it's cooked to your liking. Reserve 1 cup / 240ml of the pasta cooking water, then drain the pasta.
In a blender or food processor, blend together the pumpkin purée, tomato paste, cream cheese, and 1/2 cup of the reserved pasta water. Alternatively, you can whisk these ingredients togehter in a mixing bowl. Begin by adding hot pasta water by the tablespoon to the cream cheese, whisking as you go, so that it becomes a smooth liquid. Then, stir in the remaining sauce ingredients.
Heat the olive oil in the pot over medium low heat. Add the garlic. Cook the garlic for 30 seconds, stirring constantly, or until the garlic is fragrant and sizzling but not browning. Pour the blended pumpkin mixture into the pot, then add the pasta. Heat and stir for two minutes, or until the pasta is warmed through and saucy. If you'd like to thin the pasta sauce, add a few more splashes of pasta water to the mixture.
Top with cashew Parmesan cheese, if desired, and serve.