In a 6-quart slow cooker, finely dice the yellow onion, red bell pepper, carrot, and celery. Combine these vegetables at the bottom of the pot.

Pour in the rich tomato sauce and fire-roasted tomatoes over the diced vegetables. Stir everything together thoroughly.

Fold in the drained black beans, kidney beans, and pinto beans. Gently mix until the beans are evenly distributed.

Sprinkle kosher salt, garlic powder, ground cumin, mild chili powder, and smoked paprika into the pot. Stir well to combine all the spices.

Cover the slow cooker with its lid and set it to cook on high for 4-5 hours or on low for 6-7 hours.

Stir in fresh lime juice and any optional hot sauce before serving.