01 - Bring a large pot of salted water to a rolling boil. Add the pasta and cook according to package directions until al dente. Drain thoroughly, rinse under cold running water to halt cooking, and set aside to cool completely.
02 - While the pasta cooks, season both sides of the chicken breasts evenly with garlic powder, salt, and freshly cracked black pepper. Heat olive oil in a large skillet over medium heat. Sear the chicken for 6 to 7 minutes per side until deeply golden and cooked through to an internal temperature of 165°F. Transfer to a cutting board and rest for 5 minutes before cutting into bite-sized cubes.
03 - In a medium mixing bowl, whisk together the mayonnaise, Dijon mustard, honey, apple cider vinegar, and olive oil until completely smooth and emulsified. Season with salt and pepper to taste, adjusting as needed.
04 - In a large serving bowl, combine the cooled pasta, cubed chicken, halved cherry tomatoes, diced cucumber, diced red bell pepper, sliced red onion, and baby spinach. Pour the honey mustard dressing over the top and toss gently until every component is evenly coated.
05 - Garnish with fresh herbs if desired. Serve immediately at room temperature, or cover and refrigerate for 1 hour to allow the flavors to meld together before serving.