Add ground turkey, grated zucchini, breadcrumbs, egg, 1/2 cup chopped onion, and Flavor God seasoning to a large bowl. Mix until combined, then form 4 patties.
Grill turkey burgers until cooked through, about 10-12 minutes (I grilled mine on a George Foreman for 11 minutes at 425 degrees).
Add sliced onions to a hot, non-stick pan. Toss and continue cooking down until onions are caramelized. Add a couple tablespoons of water if needed to keep the onions moist toward the end of cooking.
Serve turkey burgers on lettuce leaves with caramelized onions and BBQ sauce.
Notes
I served this with 1 cup of grapes to make it a meal.