Preheat oven to 425 degrees. Soak potatoes in cold water for 5 minutes. Drain and dry thoroughly. In bowl, combine oil, turmeric, cumin, coriander and cayenne. Add potatoes and toss to coat. Arrange potatoes on baking sheet, bake for 20 minutes. Turn potatoes over and return to the oven for another 20 minutes. Sprinkle with salt and pepper and serve.