1 ripe avocado, sliced, or ½ cup purchased guacamole
1 medium tomato, thinly sliced
1 small red onion, thinly sliced
4 lettuce leaves
Place beans in a medium bowl and mash with a fork until mixture forms a chunky paste. Add egg, cumin, red pepper flakes, lime juice, breadcrumbs, salt and pepper, stirring until incorporated. Stir in green onions and cilantro. Add tuna and stir gently just to combine. Form mixture into 4 patties and refrigerate for 10-15 minutes.
Place oil in a large skillet over medium heat. Add patties and cook until golden brown, about 3 minutes. Turn and cook until remaining side is golden brown and patties are hot all the way through, about 3 minutes. Remove from heat and serve on buns with avocado, tomato, onions and lettuce.