2. Add onion to pot and season with salt and pepper. Cook, stirring occasionally, until soft, 8 to 10 minutes. Add ground beef and cook, stirring occasionally, just until beef is no longer pink, 10 to 12 minutes. Add garlic, chili powder, cumin, and red pepper flakes. Cook, stirring, 1 minute. Add broth, tomatoes, and browned chuck. Cover and cook, stirring occasionally, until chuck is very tender, 2 to 2½ hours.