In a large bowl, combine the ground beef, garlic, onion, pinto beans, egg and breadcrumbs. Mix until just combined.

Form the mixture into 4 patties. Season both sides of each patty with salt and pepper.

Heat the oil in a cast iron skillet over high heat. Add the burgers and cook for 5 minutes, flip and cook for 3 more minutes or until cooked through. Alternatively, burgers can be cooked on the grill.

Place the open buns on 4 separate plates. Top the bottom bun with a burger, the add sliced tomato and lettuce. Add more toppings if desired before topping with the top bun.