Step 1

Using a fork, mash the beans in a medium bowl until they are mushy but still have some whole bean pieces throughout.

Step 2

Mix the breadcrumbs, grated onion, chili powder, egg and some salt and pepper into the beans. Add a splash of water if the mixture looks dry. Set aside for 5 minutes.

Step 3

Divide the bean mixture into 4 equal balls and form into patties. Preheat a large cast-iron skillet over medium-high heat and add a few tablespoons of canola oil.

Step 4

Cook the burgers until browned, 4 to 5 minutes on each side. Add a slice of Swiss cheese to the top of each burger. Invert a second skillet on top of the first skillet and continue cooking until the cheese is melted, about 2 minutes.

Step 5

Combine the mayonnaise and a few shakes of hot sauce in a small bowl. Serve the burgers on the buns with lettuce, tomatoes and the spicy mayonnaise.