Brown the ground beef. Place a large pot over medium heat. Add the ground beef, diced onion, and minced bell pepper. Cook for approximately 10 minutes, stirring frequently and breaking the beef into small crumbles, until the meat is browned and the vegetables are tender.
Drain excess grease. Carefully drain and discard the grease from the cooked beef mixture to prevent the chili from becoming overly oily.
Add the beans and tomatoes. Stir in the pinto beans with their liquid, diced tomatoes with their juices, and tomato sauce. Mix until everything is evenly combined.
Season the chili. Add the chili powder, optional minced jalapeños, crushed red pepper flakes, ground black pepper, salt, and garlic powder. Stir thoroughly to distribute the seasonings.
Bring to a gentle boil. Increase the heat as needed and bring the mixture to a slow boil, stirring occasionally.
Simmer the chili. Cover the pot, reduce the heat to low, and let the chili simmer for at least 30 minutes. Stir occasionally to prevent the beans and tomato sauce from sticking to the bottom.
Develop the flavor. For a deeper, richer flavor, continue simmering for up to several hours, checking and stirring periodically. Add a little water if the chili becomes too thick during extended cooking.
Serve warm. Stir the chili before serving. Ladle into bowls and enjoy as a filling main dish with your favorite toppings or side dishes.