In a mixing bowl, combine olive oil, garlic powder, onion powder, salt, and pepper. Add the chicken thighs and coat them thoroughly with the seasoning mixture. Let it marinate for at least 15 minutes.
Heat a large skillet over medium-high heat. Place the marinated chicken thighs in the skillet and cook for about 6-7 minutes on each side, or until golden brown and fully cooked. Remove from the skillet and allow to rest for a few minutes.
Using a fork or a potato masher, smash the cooked chicken into bite-sized pieces.
While the chicken is resting, warm the flour tortillas in a dry skillet over medium heat for about 30 seconds on each side until pliable.
Spread a generous amount of Caesar dressing on each tortilla. Add a portion of the smashed chicken on top, followed by a handful of chopped romaine lettuce, and sprinkle generous amounts of grated Parmesan cheese over the top. Add sliced cherry tomatoes if using.
Finish off with a sprinkle of fresh parsley for garnish. Serve the tacos immediately while the tortillas are warm and the chicken is juicy.