Rinse and drain the canned black beans. Add the black beans to a food processor along with the red onion, garlic, cilantro, sriracha, mayonnaise, cumin, soy sauce, and pepper. Pulse the ingredients until they are evenly mixed, but still slightly chunky.
Transfer the black bean mixture to a bowl and add one large egg and 1 cup breadcrumbs. Stir the ingredients together until they're evenly combined. Let the mixture sit for about 5 minutes.
Divide the black bean mixture into six equal portions, then shape each portion into a patty, about 3.5 inches in diameter, ½-inch thick.
To cook the black bean burgers, heat 1Tbsp cooking oil in a skillet over medium heat. Once the oil is hot, add a few of the black bean burgers and cook for about 4-5 minutes on each side, or until they are well browned and heated through. Repeat with more oil and the rest of the patties until they're all cooked.
Place each patty in a bun, add your favorite toppings, and enjoy!