Place the drained black beans in a large mixing bowl and mash them with a fork or potato masher until mostly smooth, leaving some chunks for texture.
Add the sautéed onion and garlic to the mashed beans, and stir to combine evenly.
Mix in the breadcrumbs, cumin, smoked paprika, and the beaten egg until the mixture holds together when pressed.
Divide the mixture into four equal portions and shape each into a round patty with your hands, pressing firmly to ensure they hold together.
Heat a tablespoon of oil in a skillet over medium heat until shimmering and slightly smoking.
Carefully place the patties into the hot skillet, pressing them down slightly for even contact with the pan.
Cook the patties for about 4-5 minutes on one side, until golden brown and crispy underneath, then flip carefully with a spatula.
Cook for another 4-5 minutes on the second side until equally crispy and heated through.
Remove the patties from the skillet and let them rest for a minute to settle and firm up.
If desired, top with a slice of cheddar cheese or spread spicy mustard before serving.
Serve the black bean burgers hot, with your favorite buns, toppings, or sides for a complete meal.