For guacamole, combine lime juice and onion in a dish and let sit 15 minutes to mellow onions strong flavor. Add remaining ingredients, mashing to combine everything into a smooth mixture. Cover and refrigerate until ready to use.
For burgers, combine all ingredients together. With well oiled hands, shape into 6 patties. Chill for at least 1 hour to allow flavors to blend and patties to firm up.
Oil BBQ grate and grill burgers until fully cooked (internal temperature reaches 165°F), about 5 minutes per side.
Serve on GF buns with guacamole and any other condiments of your choice.