How to Make It
Place bread in a food processor; pulse 5 times. Transfer to a bowl.
Combine onion, garlic, juice, cumin, salt, rind, and beans in processor; pulse 4 to 5 times. Add bean mixture, walnuts, hot sauce, and egg to crumbs; stir well. Divide the mixture into 4 equal portions. Shape each portion into a 3/4-inch-thick patty.
Heat oil in a large nonstick skillet over medium-high heat. Add patties to pan; reduce heat to medium, and cook 4 minutes on each side or until browned.