1. In large skillet, heat oil over medium-high heat. Saute garlic until golden brown (30 seconds).
2. Add steak, vinegar, salt, and pepper. Cook, stirring, until beef has browned (5-6 minutes).
3. Add onion and tomato. Cook until onion is transparent (4-5 minutes). Stir in potatoes and fry until browned (3-4 minutes).