Combine 2 cans black beans and garlic in a food processor.
Cover and pulse until smooth, adding 1 to 2 tablespoons water if necessary.
Coarsely mash remaining 1 can of beans.
Combine pureed beans, mashed beans, bell pepper, breadcrumbs, cilantro, egg, salt and pepper in a large bowl, mixing well.
Shape mixture into 6 equal patties.
Heat ½ tablespoon oil in a large nonstick skillet over medium heat.
Add 3 patties to pan; cook 5 to 6 minutes per side or until browned.
Top each patty with 1 slice cheese during last 1 minute of cooking time.
Repeat procedure with remaining oil, patties and cheese.
Place 1 patty on bottom half of each bun; add salsa and bun tops.