Rub the chicken breasts all over with 1 TBSP of the olive oil then season generously all over with salt & pepper. Heat the other 1 TBSP of olive oil in a skillet over medium heat. Place the chicken in the skillet and cook on one side for 6 minutes. Flip the chicken over and cook for 5 to 8 more minutes (depending on the size of your chicken breast) or until cooked through (165°F). Lay the chicken on a cutting board and allow to cool for at least 10 minutes.
Cook the rotini according to package directions then drain and rinse under cold water.
Slice the chicken breasts into bite size pieces and add to a large mixing bowl along with the pasta, olives, tomatoes, red onion, bell pepper, and feta. Toss to combine.
Add the dressing ingredients to a jar or other container with a tight fitting lid and shake vigorously until well combined.
Drizzle half of the dressing over the pasta salad and toss to combine. Stir in more dressing to taste and season the pasta salad with extra salt & freshly ground pepper if needed.
Cover and refrigerate for at least 1 hour to allow flavors to meld. Serve cold with any leftover dressing on the side.