Begin by browning the ground meat in a skillet over medium heat until it is no longer pink and releases its aroma, about 5-7 minutes. Use a spoon to break it apart into small crumbles, then transfer the cooked meat into the slow cooker.
Add the chopped onion and minced garlic to the skillet and sauté for another 3-4 minutes until fragrant and translucent. Transfer this mixture to the slow cooker with the meat.
Pour in the canned diced tomatoes and black beans, then stir in the pumpkin purée. Mix everything well to combine the flavors evenly.
Sprinkle in chili powder, ground cumin, cinnamon, and season with salt and pepper to taste. Stir to distribute the spices throughout the mixture.
Cover the slow cooker with the lid and set it to low heat. Let the chili simmer gently for 4 hours, allowing flavors to meld and the mixture to thicken.
Once the cooking time is up, give the chili a good stir and taste for seasoning, adding more salt or spices if needed. The chili should be thick, velvety, and aromatic, ready to serve hot.
