Heat a large Dutch oven over medium-high heat. Add ground beef and cook until browned, breaking it into small crumbles with a wooden spoon for approximately 8 minutes. Drain excess fat.

Add the diced onion and bell pepper to the beef. Sauté for 5 minutes until the vegetables are translucent and softened.

Stir in the minced garlic and tomato paste. Cook for 2 minutes, stirring constantly until the tomato paste turns a deep brick red.

Add the chili powder, cumin, paprika, oregano, brown sugar, salt, black pepper, and cayenne pepper. Toast the spices for 1 minute until highly aromatic.

Pour in the crushed tomatoes, diced tomatoes with green chilies, and beef broth. Use a wooden spoon to scrape the bottom of the pot to release any browned bits (deglazing).

Stir in the drained kidney beans and pinto beans until fully incorporated.

Bring the mixture to a gentle boil, then reduce the heat to low. Cover with a lid and simmer for 45 minutes, stirring occasionally to prevent sticking.

Remove the lid and simmer uncovered for an additional 15 minutes to allow the chili to thicken to the desired consistency.

Adjust seasoning with salt and pepper to taste and serve hot with optional toppings like shredded cheddar, sour cream, and green onions.