Well, I avoid using raw pumpkin or greens in the salad. That's why spinach is also cooked for a few minutes in this recipe. However, one may definitely steam pumpkin. Since pumpkin becomes too mushy after one whistle in a pressure cooker, you may either hot boil in a large pan for about 10 min (that gives a crunchy texture to pumpkin) or make a mashed pumpkin salad.