In a large bowl, mix the ground beef, salt, pepper and garlic powder together until well incorporated.

Form into desired size beef patties.

Chill, covered, in refrigerator at least 30 minutes before grilling.

Prepare your grill.

Heat a cast iron skillet on the grill with about 1 Tbsp of Olive Oil, then add the sliced Onions and cook for about 5 minutes or until tender and starting to brown. Set aside.

You can either cook the burgers on your grill directly or indirectly using the cast iron skillet (as I did). Cook the burger patties for about 3 - 5 minutes on each side or until your desired doneness. If topping with cheese, add to burger patties and allow to melt for about 30 seconds while on the grill.

Top your Pepperidge Farm® Hamburger Buns with a slice of heirloom tomatoes, grilled burger patties, caramelized Onions, sliced Avocados and drizzle with Chimichurri sauce.