Cook pasta according to package direction. Drain and rinse with cold water, set aside.
In a small bowl or mason jar, combine the ingredients for the ranch dressing and mix/shake until combined.
In a large salad bowl, combine baby spinach, pasta, chicken, tomato, scallion, and red onion. Drizzle generously with the dressing and toss to coat.
Sprinkle with grated parmesan cheese and serve the chicken spinach pasta salad immediately.
