For the chicken: Sprinkle the chicken with salt and pepper. Heat some vegetable oil in a medium saute pan over medium heat. Add the chicken and sear on both sides. Cook until cooked through, 10 to 15 minutes, depending on size.
For the tapenade: In a bowl, mix together the olives, garlic, oil and some pepper.
For the sauce: In a small bowl, mix together the ketchup, mayonnaise, mustard, garlic salt, onion salt and pepper.
For the sandwich: Toast the hamburger bun. Place the bun on a plate and spread with some of the sauce. Layer the bottom bun with the lettuce and tomato, then add some of the tapenade. Add the chicken and top with more tapenade. Cover with the bun top and serve immediately.