To prepare chili: Heat oil in a Dutch oven over medium heat. Add onion and cook until beginning to soften, about 4 minutes. Add bell pepper and garlic and cook for 1 minute. Add beef and cook, breaking it up with a wooden spoon, until browned, 4 to 5 minutes. Stir in beans, tomatoes and their juice, chili powder, cumin, paprika and cayenne (if using). Bring to a boil; reduce heat to maintain a simmer, cover and cook until slightly thickened, about 20 minutes.