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 chopped red onion, garlic, breadcrumbs, oats, egg, cumin, smoked paprika, chili powder, salt, pepper, and cilantro. Mix until thoroughly combined.
03 - Divide the mixture into 4 equal portions and form into burger patties.
04 - Heat olive oil in a non-stick skillet over medium heat. Cook patties for 4-5 minutes per side until golden and heated through. Add cheese slices during the final minute and cover to melt if using.
05 - Lightly toast the burger buns.
06 - Spread mayonnaise and ketchup on toasted buns. Layer with lettuce, black bean patty, tomato, avocado, red onion, and pickles. Top with remaining bun.