Dice the yellow onion and green bell pepper. Mince the garlic. Drain and rinse both cans of beans. Measure out tomato sauce, diced tomatoes, and beef broth.

Brown the beef

Heat a large heavy pot or Dutch oven over medium-high heat. Add 1 tablespoon vegetable oil. When hot, add 1 lb ground beef and break it up with a spoon. Cook until no longer pink and beginning to brown, about 6–8 minutes.

Sauté vegetables

Push the browned beef to the side or remove briefly to a bowl. Add the diced onion and bell pepper to the pot and sauté in the beef drippings (add oil if needed) over medium heat until softened, about 4–5 minutes. Add the minced garlic and cook 30–60 seconds until fragrant.

Combine and simmer

Return the beef to the pot if you removed it. Stir in 15 oz tomato sauce, 14.5 oz diced tomatoes (with juices), 2 tablespoons tomato paste, and 1 cup beef broth. Add the drained kidney and pinto beans. Stir to combine and bring to a gentle simmer.

Seasonings

Add 2 tablespoons chili powder, 1 teaspoon ground cumin, 1 teaspoon smoked paprika, 1 teaspoon dried oregano, 1 teaspoon brown sugar, 1 teaspoon salt, 1/2 teaspoon black pepper, and 1/4 teaspoon red pepper flakes (if using). Stir thoroughly so the spices dissolve into the liquid.

Reduce heat to low, cover partially with a lid, and simmer gently for at least 30 minutes, stirring occasionally. For deeper flavor, simmer 1–2 hours, adding a splash of water or broth if the chili becomes too thick.

Taste and adjust seasoning before serving: add more salt, chili powder, or sugar as desired to balance acidity and heat.

To Finish / Garnish

Ladle the chili into bowls. Top each serving with shredded sharp cheddar cheese (about 2–3 tablespoons per serving) so it melts on contact.

Sprinkle sliced green onions over the cheese and add chopped cilantro if desired. Serve hot with optional accompaniments such as cornbread or tortilla chips.