Gather ingredients.
Heat olive oil in a 4- to 5-quart Dutch oven over medium-high heat. Add onion and tomato paste; cook, stirring until tomato paste begins to darken and onion is tender, 4 to 5 minutes. Add garlic, stirring until fragrant, about 30 seconds.
Pour broth into Dutch oven. Add bell pepper, squash, diced tomatoes, and roasted tomatoes. Stir in brown sugar, chili powder, cumin, and crushed red pepper, if using. Cover, reduce heat to medium-low, and simmer until squash is tender, 20 to 25 minutes.
Add beans and ground meat (if using) to pot. Cover and simmer until flavors have developed, about 15 minutes. Season with salt and pepper.
Top with cheese, sour cream, cilantro, jalapenos, and avocado, as desired.