2 (15-oz) cans black beans, rinsed and drained
1/2 medium yellow onion, chopped
2 cloves garlic, minced
1 large egg
1/2 c. plus 2 tbsp. mayonnaise, divided
3/4 c. panko bread crumbs
Freshly ground black pepper
2 tbsp. canola oil
4 slices white cheddar
3 tbsp. ketchup
4 hamburger buns
1 tomato, sliced
4 Romaine lettuce leaves
In a food processor, pulse black beans, onion, and garlic until finely chopped.
Transfer to a large bowl and combine with egg, 2 tablespoons mayonnaise, and panko. Season generously with salt and pepper and form the mixture into 4 patties. Refrigerate until firm, about 15 minutes.
In a large skillet over medium heat, heat oil. Add patties and cook until golden and warmed through, about 5 minutes per side.
Top each patty with a slice of cheese and cover the skillet to melt.
In a small bowl, whisk together ketchup and remaining 1/2 cup mayonnaise. Spread mixture onto bottom buns, then add burgers. Top with tomato, lettuce, and remaining bun halves.