To prepare burgers, heat oil in a large nonstick skillet over medium-high heat.
Combine kidney beans and black beans in a large bowl; partially mash with a fork. Add breadcrumbs, corn, onion, and egg; stir until well blended. Form bean mixture into 4 (1/2-inch-thick) patties. Add patties to pan; cook 4 minutes on each side or until crisp and beginning to brown.
To prepare ketchup, combine ketchup, honey, lime juice, chile powder, and cumin, stirring with a whisk.
Spread 1 tablespoon ketchup on bottom half of each bun; top each serving with a patty, 1 lettuce leaf and 1 tomato slice (if desired), and top half of bun.