- 2 tablespoons reduced-fat mayonnaise
- 2 teaspoons ketchup
- 2 teaspoons chopped capers
- 1 teaspoon chopped pickle, or relish
- 3 teaspoons extra-virgin olive oil, divided
- 1 small red onion, thinly sliced
- 1 cup sliced mushrooms
- 5 cups baby spinach
- Freshly ground pepper, to taste
- 4 slices rye bread
- 1/2 cup shredded reduced-fat Swiss cheese, such as Jarlsberg Lite or Alpine Lace (2 ounces)
- 1/2 cup sauerkraut
- Prepare Russian dressing: Whisk mayonnaise and ketchup in a small bowl until smooth. Stir in capers and pickle (or relish).
- To prepare sandwiches: Heat 2 teaspoons oil in a large nonstick skillet over medium-high heat. Add onion and mushrooms; cook, stirring often, until the onion is softened, 4 minutes. Add spinach and cook, stirring, until it has wilted, 1 to 2 minutes. Transfer the mixture to a plate.
- Coat the pan with the remaining 1 teaspoon oil and return to medium heat. Add the bread; divide cheese equally among the slices. Divide sauerkraut between 2 slices and divide the spinach mixture between the other 2 slices; cook until the cheese has melted and the bread is golden brown, 4 to 6 minutes. Transfer sandwich halves to a cutting board. Divide the dressing between the spinach halves. Carefully place the sauerkraut halves on top. Cut sandwiches in half and serve.