First, prepare the Yogurt Sauce.
In a small bowl, stir together the plain yogurt, 1 tablespoon (15 ml / 0.5 fl oz) of cilantro, and lemon juice.
Cover and chill in the refrigerator while you prepare the burgers.
To make the patties, combine the rinsed garbanzo beans, beaten eggs, and chopped red onion in a large bowl. Use a potato masher to mash the into a coarse paste. Alternatively, you can pulse them in a food processor until a coarse paste forms, then transfer to a large bowl.
Stir in the crushed crackers, 1/4 cup (960 ml) cilantro, lemon peel, and salt until everything is well combined.
Lightly wet your hands to prevent sticking and shape the mixture into eight 1/2-inch-thick patties.
Arrange the patties on a tray or large plate, then brush both sides with olive oil.
Cover and chill for at least 30 minutes to help them firm up.
Preheat your grill to medium heat and grease the rack well. For a charcoal grill, arrange medium coals for direct heat.
Place the chilled patties directly on the greased rack.
Grill for 10 to 12 minutes, uncovered, flipping once halfway through, until the patties are golden brown and heated through.
Assemble your burgers!
Serve by layering avocado slices, tomato, and roasted red peppers on four of the patties.
Drizzle generously with the chilled Yogurt Sauce and top with the remaining four patties to create delicious, double-stacked burgers.
Add a teaspoon of ground cumin or smoked paprika to the patty mixture for a deeper, smokier flavor profile.
