Seed and peel the pumpkin, then cut into rectangular chunks about 2-inches by 3-inches. Place the pumpkin pieces in a wide heavy pan, sprinkle with the sugar, and cover with the water and lemon juice. Cover the pan and cook over low heat for 1 hour, until pumpkin flesh is tender, occasionally basting with the juices.
Remove pan from the heat and let pumpkin cool in the liquid. Remove pumpkin pieces and arrange on a serving dish. Spoon the syrup from the pan over the pumpkin, drizzle with the tahini and sprinkle with the ground walnuts.
c.1997, M.S. Milliken & S. Feniger, all rights reserved