Black Bean Smash Burgers with Caramelized Onions

For burger sauce, in a food processor, combine tofu, ketchup, red wine vinegar, mustard, and garlic powder. Process until smooth. Stir in dill pickle relish. 2. For patties, in a food processor combine bell pepper, ¼ cup of the onions, and the garlic. Pulse until finely chopped. In a large bowl mash ¾ cup of the black beans with a potato masher or fork until nearly smooth. Stir in remaining beans, bell pepper mixture, panko, cumin, and ½ teaspoon of the black pepper. Divide the mixture into four portions and shape into ½-inch-thick patties. Transfer to a tray lined with parchment paper; gently smash patties with a burger press or spatula to ¼-inch thickness. Chill at least 1 hour or up to 4 hours. 3. Meanwhile, for caramelized onions, heat a large skillet over medium. Add the remaining 2 cups onions and 2 tablespoons water. Cook over medium 15 minutes or until onions are softened and deep golden brown, stirring occasionally and adding water, 1 tablespoon at a time, as needed to prevent sticking. Season with paprika and the remaining ¼ teaspoon black pepper; cook 1 minute more. Keep warm. 4. Heat a griddle over medium-high. Add patties; cook 8 minutes or until browned, carefully turning once halfway through cooking. Layer lettuce and tomato on bun bottoms, and top with patties. Top each patty with onions, about 1 tablespoon of the burger sauce, and bun tops. Store leftover burger sauce in the refrigerator up to 5 days.