Mash the drained black beans in a large mixing bowl until mostly smooth but with some chunks remaining for texture.
Add the finely diced onion, ground cumin, lime juice, salt, and black pepper to the mashed beans. Mix thoroughly until all ingredients are well combined and the mixture is cohesive.
Stir in the panko breadcrumbs gradually, mixing until the mixture holds together when pressed. If too wet, add a little more breadcrumbs; if too dry, a squeeze of lime juice helps loosen it.
Divide the mixture into four equal portions and gently shape each into a round patty about 1/2 inch thick using your hands.
Heat the olive oil in a skillet over medium heat until shimmering and slightly aromatic.
Place the patties into the hot skillet carefully, giving them space, and cook for about 4-5 minutes per side until golden brown and crispy on the outside.
Flip the patties gently with a spatula to ensure even browning, and cook the other side until similarly crisp and heated through.
Remove the cooked patties from the skillet and let them rest for a minute to firm up slightly.
Serve the patties hot, as a burger on buns or alongside your favorite sides, enjoying their hearty yet tender texture with bright, earthy flavors.
