Roast beef, vegetables, and soba noodles make this recipe a complete meal that can be made in about 20 minutes.
Bring stock and soy sauce to a boil on medium-high heat. Stir in beef and noodles. Return to boiling; reduce heat, cover, and simmer for 3 minutes.
Add carrots and broccoli. Simmer 2 to 3 minutes more, then stir in spinach and cilantro.