How to Make It
Place Greek yogurt, ketchup, 2 tablespoons sauerkraut, and mustard in a mini food processor; process until smooth.
Cut tempeh in half horizontally; cut each half into 4 slices, forming 8 pieces. Heat a large skillet over medium heat. Add oil to pan; swirl to coat. Add onion; cook 5 minutes or until tender. Add garlic; cook 1 minute, stirring constantly. Add vinegar, soy sauce, dill, and caraway, stirring constantly. Add tempeh; cook 1 minute on each side. Add 1 1/4 cups water; bring to a boil. Reduce heat; simmer, uncovered, 10 minutes or until water evaporates, turning tempeh occasionally.
Preheat broiler to high. Place 4 bread slices in a single layer on a heavy baking sheet. Divide cheese evenly among bread slices. Broil 1 minute or until cheese melts. Top cheese with about 1 tablespoon yogurt mixture, 1 1/2 tablespoons onion mixture, 2 pieces tempeh, and about 3 tablespoons sauerkraut. Spread remaining yogurt mixture evenly over 1 side of remaining 4 bread slices. Place bread, yogurt side down, on top of sauerkraut.