Cook pasta according to package directions; drain. Meanwhile, trim fat from meat. Thinly slice beef across the grain into bite-size strips.
In a large skillet cook and stir beef in hot oil for 2 to 3 minutes or until desired doneness. Add pasta sauce, salt, and cinnamon. Cook and stir until sauce is bubbly. Add cooked pasta and spinach. Cook and stir until heated through. Sprinkle individual servings with feta cheese. Makes 4 servings.