Heat a large pot over medium heat and add the oil. Once the oil is heated, add the onion and bell pepper. Sauté, stirring occasionally, until mostly tender, about 5 minutes.
Stir in the pumpkin puree, tomatoes, taco seasoning, rigatoni, broth, and water. Cover and bring to a low boil. Cook, stirring every 3-5 minutes, until the pasta is cooked through, about 20 minutes.
Stir in the sour cream and oaxaca and let melt for a couple minutes.
