Preheat oven to 425 degrees. In a large oven-proof skillet over medium heat, saute kielbasa until browned, about 4 minutes on each side. Remove kielbasa to a plate and keep warm. In the same pan, saute the onion and the apple for 1 minute. Drain and rinse the sauerkraut and add it to the apples and onion in the skillet. Add the chicken stock and caraway seeds to the pan and stir. Return the kielbasa to the skillet and cover. Put covered skillet in hot oven and cook for 15 to 20 minutes.