Mix: pumpkin puree, ½ cup sugar, half and half, vanilla, butter, baking powder, salt, pumpkin spice. Add flour slowly, ¼ cup at a time, mixing each time. Pour into baking dish.
Mix topping: brown sugar, ½ cup sugar, pecan. Spread topping over batter in dish. Pour boiling water over it.
Bake in pre-heated oven at 350 degrees F for 45-60 minutes