Boiling salted water and cook pasta al dente according to the package. Once done, drain, and then pour into a bowl of ice water to cool it down quickly. Drain off the water and place in a large mixing bowl.
While the pasta boils, cook the chicken. Season both sides of chicken breasts with salt and pepper. Cook on a medium-high grill or skillet on both sides until center is 165˚F. (About 5 minutes per side, depending on thickness.) Let cool and then slice.
Assemble by placing pasta, chicken, tomatoes, and spinach** together in a large bowl. Pour the dressing over the top. Sprinkle with parmesan cheese, toss and serve.
For the Dressing:
In a jar or liquid measuring cup, whisk together the olive oil, vinegar, dijon mustard, basil, oregano, garlic powder, salt and pepper.
*You can substitute with leftover chicken, rotisserie chicken, or buy precooked grilled chicken.**If you do not plan to eat the pasta right away, add everything to the bowl EXCEPT the dressing or the spinach. Once the spinach gets wet it will wilt quickly so either keep the dressing in a jar or the spinach in a bag.