Make the dressing: In a bowl, combine the mayonnaise, grated Parmesan, olive oil, lemon juice, chopped capers, Dijon mustard, garlic, Worcestershire sauce, salt and pepper. Whisk until smooth and well combined. Set aside half the dressing in the refrigerator for 30 minutes.
Marinate the turkey: Place the turkey breasts in a shallow dish. Coat generously with the other half of the Caesar dressing and refrigerate for 30 minutes.
Make the crispy breadcrumbs: In a skillet, melt the butter over medium heat. Add the drained and dried capers, then cook for 2 minutes until they start to crisp up slightly. Add the panko breadcrumbs, garlic and onion powder. Cook, stirring regularly, for 2 minutes or until the breadcrumbs are golden. Remove from heat and set aside.
Preheat the grill: Heat the barbecue to high and oil the grates.
Grill the turkey: Place the turkey breasts on the grill and cook for 6 minutes per side, or until the internal temperature reaches 74°C (165°F). Remove from the grill and let rest a few minutes before slicing.
Grill the romaine and lemons: Place the quartered romaine hearts and lemon halves on the grill. Cook for 2 minutes until nice grill marks appear.
Assemble the salad: Arrange the grilled romaine hearts on a large serving platter. Add the turkey slices and grilled lemon halves, then drizzle generously with the remaining Caesar dressing.
Garnish and serve: Sprinkle with grated Parmesan and the crispy caper breadcrumbs. Serve immediately.