Prepare the Patty Mixture: In a large mixing bowl, combine the ground turkey, egg, chopped red onion, diced red bell pepper, Dijon mustard, onion powder, garlic powder, chopped parsley, kosher salt, and freshly ground black pepper. Gently mix without overworking the meat.

Shape the Patties: Divide the turkey mixture into 4 to 6 equal portions and shape into patties. Place on a parchment-lined tray.

Chilling the Patties: Chill patties in the refrigerator for at least 15 minutes to maintain shape while cooking.

Cook the Patties: Heat olive oil in a skillet over medium-high heat. Cook patties for about 5 minutes on one side until golden brown, then flip and cook for another 5 minutes.

Prepare the Zucchini: Slice zucchini, toss with olive oil, salt, and pepper. Grill for about 2 minutes on each side until tender.

Assemble the Burgers: Use a large iceberg lettuce leaf as a base, add a turkey patty, zucchini, and optional red onion slices. Top with another lettuce leaf to create your 'bun'.

Serve and Enjoy: Serve immediately and consider pairing with sweet potato fries or a cucumber salad.