Prepare 2 pastry-lined pie plates. Mix rhubarb and apples together, then divide them equally into the pie plates. Mix dry ingredients and once again divide the mixture into the two pies. Drizzle ¼ cup of molasses over each pie and dot with butter.
Cover pies with pastry and bake at 400°F for 20 minutes, then at 375°F for 40 minutes.
