01 -
Slice the tempeh in half lengthwise, then cut each half crosswise to yield four thin rectangles. Place the pieces in a saucepan, add enough water to cover, soy sauce, salt, and smoked paprika. Cover and simmer for 10 minutes. Drain and pat the pieces dry.
02 -
In a small bowl, whisk together mayonnaise, ketchup, paprika, lemon juice or vinegar, salt, and pepper. For added depth, blend in garlic, horseradish, and a splash of Worcestershire or soy sauce if desired.
03 -
In the same pan, wipe dry and heat olive oil over medium-high. Sear tempeh slices on each side until deeply golden and crisp, approximately 2–3 minutes per side. Reduce heat, add cheese slices atop the tempeh, and cover until the cheese is thoroughly melted. Remove from heat.
04 -
Toast the sourdough rye slices either in a toaster or in the skillet with a touch of olive oil until golden and crisp.
05 -
Generously spread Reuben sauce or mustard on all bread slices. Layer tempeh, sauerkraut, and top with the remaining bread. Slice each sandwich in half if desired and serve warm.