Peel and chop onion and garlic. In a large skillet on medium heat, add 1 tablespoon of oil and add onion. Cook until soft and nearly translucent, about 5 minutes. Add garlic and cook until fragrant. Remove veggies to large crock pot. In the same skillet add the remaining 1 tablespoon oil and ground beef. Add the spice and cook until just brown. When just barely browned, add to crock pot. Add 1 large can of diced tomatoes (with liquid). Add beef broth. Stir together and cook on low for about 6 hours. About 30 minutes before service, add beans to warm through (beans will be mushy and overcooked if added in the beginning). If desired, served topped with sour cream, shredded Cheddar or Monterey Jack cheese, sliced green onions.