Pat the black beans dry and place them in a large bowl. Use a fork or potato masher to mash the black beans until they are mostly mashed but there are still some larger pieces of beans left in the mixture. Add the panko breadcrumbs, red bell pepper, green onions and garlic to the bowl with the beans.
In a medium bowl, combine the egg, ketchup, smoked paprika, cumin, chili powder, salt and black pepper. Use a whisk to mix until well combined.
Pour the egg mixture into the bowl with the black beans, using a small spatula to scrape all of the egg and spices into the bean mixture. Stir with a fork until everything is well combined.
Divide the mixture into 4 equal portions and then shape each portion into a burger that is about ½-inch thick.
To cook on the stove: Heat about 1 tablespoon of olive oil in a cast iron skillet, nonstick skillet or grill pan over medium heat. Cook the black bean burgers in the hot pan for 4-7 minutes per side, or until the burgers are browned on the outside and reach at least 160° F in the center.
To cook in the oven: Preheat oven to 375° F. Place burgers on a parchment paper-lined baking sheet. Bake for 13-15 minutes, flipping burgers over halfway through the cook time. Burgers are done when the center registers at least 160° F on an instant read thermometer.
To cook on an outdoor grill: Make sure the grill grates are clean and preheat a gas or charcoal grill to medium heat. Oil the grill grates well and cook burgers for 4-7 minutes per side, until burgers reach at least 160° F in the center. You may wish to use a grill topper or grill basket to ensure that the burgers hold their shape, as they can be more delicate than meat burgers.
Serve black bean burgers on burger buns with toppings, as desired.