You can carry the warmth of a family dinner into the week with this Asian twist on leftover roast beef.
In a large skillet over medium heat, heat oil. Cook onion, garlic, and red pepper until onion is translucent, about 2 minutes. Add soy sauce; cook until evaporated, about 2 minutes.
Turn off heat; stir in eye of round slices until heated through. Stir in peanuts, vinegar, and cilantro. Serve in Boston lettuce cups.