Preheat oven to 350 degrees F (175 degrees C). Place cranberries in a shallow 1 1/2 quart baking dish. Sprinkle with sugar, cover with foil and bake for 35 minutes. Remove from oven and sprinkle with walnuts. Re-cover and bake for 10 minutes. Remove from oven and stir in marmalade and lemon juice. Mix well. Cool to room temperature. Cover tightly and refrigerate at least 3 hours before serving.