Heat oven to 375°. Coat a 10 x 10 x 2-inch baking dish with nonstick cooking spray.
Melt butter in a medium nonstick skillet over medium heat. Add onion and cook 5 minutes. Remove from heat and transfer to a bowl with a slotted spoon. Stir sauerkraut and caraway seeds into onion and toss to mix. Return skillet to heat and add wine. Heat through, 1 minute.
Thinly slice potatoes with a food processor, V-slicer or mandoline. Begin layering: Spread a layer of potatoes (1/3 of the slices) on the bottom of prepared dish, overlapping slightly. Top with half of the sauerkraut mixture and half of the kielbasa.
In a medium bowl, toss Swiss cheese with cornstarch. Pour half of the wine over the kielbasa, then top with half the cheese. Add a second layer of potatoes, and the remaining sauerkraut and kielbasa. Pour remaining wine over kielbasa, then fan remaining potatoes over kielbasa. Sprinkle with remaining cheese.
Coat a sheet of foil with nonstick spray and cover dish. Bake, covered, at 375° for 40 minutes. Uncover and bake an additional 20 minutes, or until potatoes are tender.