Boil a salted pot of water for your pasta and cook it al dente according to package directions.
Meanwhile, cut the chicken breasts in half lengthwise so you get 4 thinner pieces. Season them with the garlic powder, 1/2 tablespoon ranch seasoning, and some pepper.
Add the oil to a skillet and let it heat up for a few minutes. Cook the chicken about 5-6 minutes/side or until it's golden and cooked through (165F). Transfer the chicken to a plate.
Reduce the heat to medium, then add the butter to the skillet. Once it's melted, add the flour and cook for 1 minute.
Stir in the garlic, followed by the chicken broth, lemon juice, and remaining 1/2 tablespoon of ranch seasoning (whisk until smooth).
Stir in the tomatoes and continue cooking the sauce until it's reduced a bit (3-5 minutes).
Meanwhile, cut the cooked chicken up into bite-size strips.
Add the spinach to the skillet and stir/toss and let it wilt for a minute or two, then add the chicken in along with the drained pasta and toss until coated.
Serve with parmesan and parsley if desired, and enjoy immediately.