1. In a bowl, combine chicken and vinegar, mix to coat chicken, cover and set aside.
  2. Cook pasta as per packet directions. Once cooked drain and set aside.
  3. In a large skillet over a medium-high heat, warm olive oil and cook onion, stirring for 3 to 4 minutes, until softened but still tender. Add the garlic, sauté 1 minute then add the mushrooms and cook, stirring for 2 minutes.
  4. Add lemon juice, tomatoes and chicken with vinegar to the skillet. Bring to a light boil, then reduce heat to medium and cook for 8 to 10 minutes until chicken is cooked through, stirring occasionally. Just before serving add capers then pour sauce over pasta. Combine sauce and pasta and serve in bowls.