Heat the olive oil in a large pot or Dutch oven over medium heat. Add the diced onion and sauté until translucent, about 5 minutes.
Add the minced garlic and diced bell pepper. Sauté for another 2-3 minutes until fragrant and the bell pepper is slightly softened.
Stir in the ground cumin, chili powder, and smoked paprika. Cook for another minute, allowing the spices to release their fragrance.
Add the pumpkin puree, kidney beans, black beans, diced tomatoes (with juice), and vegetable broth to the pot. Stir well to combine all ingredients.
Season with salt and pepper to taste. Bring the chili to a simmer, then reduce the heat to low and cover the pot. Let it simmer for about 20-25 minutes, stirring occasionally.
Taste and adjust seasoning if necessary. If the chili is too thick, you can add more vegetable broth to reach your desired consistency.
Serve hot, garnished with optional toppings like sour cream, shredded cheese, avocado, or cilantro.