Brown the beef. Heat 1 tablespoon olive oil in a large Dutch oven or heavy-bottomed pot over medium-high heat. Add the ground beef and cook, breaking it up with a wooden spoon, until browned and cooked through. Remove the beef from the pot and set aside.
Cook the vegetables. Add 2 tablespoons of olive oil to the pot. Add the diced onion and bell pepper and cook for 6–8 minutes, stirring occasionally, until the onion is soft and the pepper is beginning to soften.
Bloom the spices. If the pot looks dry, add another 1-2 tablespoons of olive oil. Add the chili powder, cumin, smoked paprika, onion powder, garlic powder, black pepper, salt, and cinnamon. Stir constantly and cook for 30–60 seconds, until the spices are very fragrant.
Add the garlic and tomato paste. Add the minced garlic and cook for about 30 seconds. Add the tomato paste and stir it into the vegetables and spices. Cook for 1–2 minutes, stirring frequently. The tomato paste should darken slightly and become fragrant.
Build the chili. Return the browned beef to the pot. Add the pumpkin purée, diced tomatoes, tomato sauce, beans, broth, and brown sugar. Stir everything together, scraping up any flavorful bits from the bottom of the pot. Bring the chili to a gentle boil, then reduce the heat to low.
Simmer. Cover partially and simmer for 15-30 minutes, stirring occasionally. For an even thicker and more flavorful chili, you can simmer uncovered toward the end. If it becomes thicker than you'd like, add a little more broth.
Balance the flavor. Remove from the heat and stir in 1 tablespoon apple cider vinegar. Taste and adjust the seasoning. You want the finished chili to taste savory and rich, with the pumpkin adding body and a subtle sweetness—not like pumpkin pie.
