In a bowl, combine the garlic powder, onion powder, smoked paprika, Italian seasoning, kosher salt, freshly ground black pepper, and olive oil to create the chicken marinade.

Pat dry the chicken breasts with paper towels to ensure better adherence of the seasoning and promote grill marks. Coat both sides of the chicken breasts with the marinade mixture.

Combine the sliced tomatoes, diced red onion, jalapeno pepper, diced cucumber, diced avocado, chopped cilantro, lime juice, kosher salt, and freshly ground black pepper in a large mixing bowl. Gently toss to combine. To prevent the avocado from browning, add the avocado pit to the salsa.

Preheat the grill to medium-high heat (375 to 450 degrees F). Grease the grill grates with non-stick cooking spray. Place the marinated chicken breasts on the preheated grill and close the lid. Cook each side for approximately 6 to 7 minutes, or until the internal temperature reaches 165 degrees F.

Let the grilled chicken rest for 5 minutes before slicing. Serve topped with the avocado salsa.