Place chicken breasts and caesar dressing in a large ziplock bag and allow to marinade for at least 4 hours up to overnight.
In a large skillet, cook bacon until browned and crisp. Remove bacon from the pan and place on paper towels to drain.
Leaving the bacon grease in the pan, heat over medium-high heat and cook the chicken breasts for about 2 minutes per side or until they get some color on them. They do not have to be cooked through, just browned. Remove chicken from pan and set aside.
Pour off all but 2 tbsp of the bacon grease from the pan, return to the heat and cook the onions and mushrooms until tender and caramelized-- about 3-5 minutes.
Sprinkle flour over the mushrooms and onions and stir until combined. Slowly pour the chicken broth into the pan, stirring constantly until no lumps remain. Stir in the salt and pepper and break the pasta in half, placing it in the pan. Arrange the chicken on top of the pasta, bring the pan to a boil, cover and reduce heat to low. Cook for 6-8 minutes or until the pasta is tender and chicken is cooked through.
Remove chicken from pan once again and add the cream, lemon juice, cheese, tomato and parsley to the pasta. Stir to combine and place the chicken on top of the pasta to serve