Place ground beef and onion in a large skillet. Start browning the meat and add seasonings. Continue to cook until beef is fully cooked and onions are tender; drain. Stir in green beans, tomato and beef stock. Bring to a boil, reduce heat to low and simmer about 10-15 minutes, until green beans are crisp-tender and stock is reduced. Stir in tomato paste and continue to cook another 5 minutes, until sauce is thickened.
Notes
This tastes great served over cooked pasta, rice or mashed potatoes. If you want to turn it into a one dish dinner, up the beef stock to 4 1/2 cups total and stir in the pasta with the green beans. Then, cover while simmering, until noodles are cooked. Good stuff!