Preheat oven to 350°F. Toss together onion, oil, soy sauce, and garlic salt on a rimmed baking sheet; spread in single layer. Bake 30 minutes or until onion is very tender, turning after 15 minutes; cool slightly.
Meanwhile, cook patties in a cast-iron skillet 5 to 6 minutes per side or until no longer pink, topping with cheese during last 3 minutes of cooking.
Serve burgers in lettuce leaves topped with tomato and onion.
Side Dish Instructions
Toss together zucchini, eggs, paprika, garlic salt, and pepper in a large bowl. Add cheese crisps and panko; toss.
Spread in a single layer on large rimmed baking sheet lined with parchment paper. Bake 25 to 30 minutes or until zucchini is golden, turning after 10 minutes. Serve with ketchup for dipping.