First, Prep The Chicken. In a medium bowl, combine diced chicken with the Cajun seasoning and stir to combine. The chicken should be generously and evenly coated in seasoning.
Cook Chicken. Heat olive oil in a large, deep skillet with a lid over medium heat (I use a 12-inch skillet with tall sides--you can also use a Dutch oven if you don't have one!). Add chicken and cook 4-5 minutes per side, or until chicken is browned on the bottom and cooked about halfway through. Flip the chicken over and cook the other side until chicken is fully cooked through. )The interior should read 165 degrees F on an instant read thermometer.) Set cooked chicken aside on a clean plate.
Build Flavor. Add the butter to the skillet, along with the onion and cook 5-7 minutes or until the onion is tender and translucent. Add sun-dried tomatoes, tomato paste, garlic, and salt to the skillet and cook 2-3 minutes more.
Cook Orzo. Add 2 1/2 cups of chicken broth to the skillet and scrape up any browned bits from the bottom of the pan. Bring the broth to a boil over medium-high heat and add orzo pasta. Reduce heat to a simmer and cook 10-15 minutes, or until the orzo is tender, adding more broth 1/4 cup at a time, as needed. (I usually use about 3 1/2 cups broth total, since the pasta will continue to absorb liquid.)
Finish The Dish. Add cream, parmesan, spinach, and the cooked chicken to the skillet and stir 2-3 minutes, until the orzo mixture is evenly combined and the spinach has wilted. Garnish with fresh herbs and serve right away!
Store leftovers in an airtight container 3-4 days in the fridge and reheat in the microwave or on the stovetop.