Add the remaining 1 tablespoon oil to the pan. Add onion and apple and cook, stirring constantly, until beginning to brown, 1 to 2 minutes. Add cabbage, carrot, vinegar and salt and cook, stirring often, until just wilted, about 2 minutes. Add cider and caraway seeds; bring to a boil. Return the sausages to the pan and reduce heat. Cover and simmer until the sausages are heated through and the cabbage is tender, about 10 minutes.