Mash black beans with potato masher in medium bowl until almost smooth. Add bread crumbs, Egg Beaters, Cajun seasoning and salt; mix until blended. Shape mixture into 6 patties, about 1/2-inch thick.
Heat 1 tablespoon oil in large skillet over medium-high heat. Add 3 patties; cook 3 minutes on each side or until set and hot. Remove from skillet; keep warm. Add remaining 1 tablespoon oil and repeat with remaining patties. Remove from heat.
Spread 1 tablespoon guacamole on bottom half of each bun. Top each with a patty and 1 tomato slice. Close with tops of buns. Serve immediately.