COMBINE lettuce, onions and cilantro. Refrigerate until ready to use. Meanwhile, mix steak sauce and barbecue sauce in medium bowl, then mix seasonings in separate bowl.
FOR each serving: Deep fry 6 plantain slices in 350ºF oil 1 min.; remove from oil. Flatten each slice to 2-inch round. Return to oil; fry 2 min. or just until plantains are caramelized; drain. Season with salt; cover to keep warm.
RUB about 1/2 tsp. seasoning mixture evenly onto both sides of each of 3 beef patties; cook on medium-high heat 5 min. on each side or to medium (160ºF) or desired doneness.
COVER each of 3 fried plantain slices with 1 Tbsp. lettuce mixture, about 1/4 tsp. hot sauce, 1 burger, 1 tomato slice and about 1 tsp. steak sauce mixture. Cover with remaining fried plantain slices.