01 - Mash the black beans in a large bowl using a fork or potato masher until mostly smooth, leaving some chunks for texture.
02 - Add the chopped red onion, garlic, breadcrumbs, oats, egg, cumin, smoked paprika, chili powder, salt, pepper, and cilantro. Mix until well combined.
03 - Divide the mixture into 4 equal portions and shape into burger patties.
04 - Heat olive oil in a non-stick skillet over medium heat. Add the patties and cook for 4–5 minutes per side, until golden and heated through. Add cheese slices during the last minute if using; cover to melt.
05 - Toast the burger buns lightly.
06 - Spread mayonnaise and ketchup on the buns, then layer with lettuce, black bean patty, tomato, avocado, red onion, and pickles if desired. Top with the remaining bun.
07 - Serve hot with your favorite sides.