Dice the onion and chop the smoked bell pepper into small pieces, preparing them for sautéing.
Heat the olive oil in a skillet over medium heat. Add the diced onion and sauté for about 3-4 minutes until it becomes translucent and fragrant.
Add the chopped smoked bell pepper and minced garlic to the skillet. Cook for another 1-2 minutes, stirring gently, until the mixture is fragrant and the peppers soften slightly.
Transfer the sautéed vegetables from the skillet into the slow cooker, spreading them evenly at the bottom.
Pour in the canned diced tomatoes along with their juices, then add the canned pumpkin and drained beans to the slow cooker.
Stir in chili powder, ground cumin, cayenne pepper if using, and season with salt and pepper to taste. Mix everything thoroughly to combine all the flavors.
Set the slow cooker to low and cook uncovered for 5-6 hours, stirring occasionally. The chili should thicken, and the flavors will meld into a rich, earthy aroma.
Once cooked, taste and adjust salt and pepper if needed; the chili should be thick and velvety, with a warm orange hue.
Spoon the hearty pumpkin bean chili into bowls, and enjoy the comforting, flavorful dish with your favorite toppings or sides.
