Pound the chicken breasts to about 1/2-inch thickness.
In a small bowl, mix garlic powder, onion powder, paprika, black pepper, and salt. Sprinkle over the chicken and press lightly.
Heat olive oil in a skillet over medium-high heat. Cook the chicken for 5–7 minutes per side, or until it reaches 165°F (74°C) internally.
Let the chicken rest for 5 minutes, then dice into bite-sized pieces.
Bring a large pot of salted water to a rolling boil.
Add the pasta and cook for 8–10 minutes, until al dente.
Drain and rinse the pasta with cold water to stop the cooking. Spread it out and let it cool completely.
In a large bowl, whisk together mayonnaise, Parmesan cheese, Caesar dressing, lemon juice, Dijon mustard, minced garlic, black pepper, and salt. Add milk or cream if needed to thin the dressing.
Add the cooled pasta and toss to coat evenly.
Add the diced chicken, romaine lettuce, cherry tomatoes, and red onion. Toss gently to combine.
Cover and refrigerate for at least 30 minutes.
Just before serving, toss in the croutons and serve chilled.