Preheat oven to 350 degrees. Bring a large pot filled three-quarters full with water to a boil over high heat. Reduce heat to a simmer and add kielbasa; cook 15 minutes.Advertisement
Transfer kielbasa to 2 baking sheets. Pour 1/2 cup of the cooking liquid over each ring of kielbasa. Using a fork, poke holes all over the top. Roast until the skin is crackling and just beginning to brown, about 20 minutes.
Slice kielbasa on the diagonal into 1/2-inch-thick slices. Serve with rye bread and horseradish.