Start by chopping the onion and mincing the garlic to prepare their flavors for the chili.
In a large skillet over medium heat, cook the ground meat until browned and cooked through, breaking it apart with a spoon.
Transfer the cooked meat to the slow cooker, then add the chopped onion and minced garlic, stirring to combine.
Add the drained black beans, corn, diced tomatoes, and pumpkin puree into the slow cooker, stirring everything together until well combined.
Sprinkle in the chili powder, cumin, cinnamon (if using), and season with salt and pepper to taste.
Stir all ingredients thoroughly to evenly distribute the spices and pumpkin, then cover the slow cooker with the lid.
Set the slow cooker to low and cook the chili for 6 hours, allowing the flavors to meld and the mixture to thicken slightly.
Once finished, open the lid and give the chili a good stir. It should be fragrant, thick, and bubbling gently.
Ladle the hot chili into bowls and serve with optional toppings like sour cream, shredded cheese, or fresh cilantro.
