Sauté the veggies. Heat olive oil in a Dutch oven or a large pot set over medium-high heat. Add onions and bell pepper, and cook for about 5 minutes or until tender, stirring frequently. Add the minced garlic and cook for 20 seconds or until fragrant.
Brown the beef. Add the ground beef to the pot and cook it until browned, breaking the meat lumps during the cooking process. It should take around 6-8 minutes over medium-high heat. Season to taste with salt and pepper and cook for 5 more minutes.
Add the remaining ingredients. Stir in the black beans, pinto beans, chopped tomatoes, pumpkin puree, tomato juice, chili powder, cumin powder, paprika and cinnamon.
Cook. Simmer the chili over medium heat for 30-35 minutes or until the flavors are blended. Remove from heat and let it rest for a few minutes.
Enjoy! Serve the pumpkin chili warm, garnished with some sour cream, cheddar cheese, and jalapeno slices.