In a large bowl combine the flour, salt, and sugar. Add the butter and cut with a pastry blender until the mixture looks like sand with large pebbles.
Add the water a tablespoon at a time until the dough just holds together. Shape into a ball and refrigerate for an hour or freeze for 30 minutes.
If roasting pumpkins for puree, if not skip down to next section
Preheat the oven to 400°F or gas mark 6.
Cut the top off of the pumpkin and then cut the pumpkin in half.
Scoop out the seeds and place on the pumpkin cut side down on the lined sheet pan. Roast for an hour.
Remove the skin and puree in a blender until smooth.
Making the filling
Preheat the oven to 350°F or gas mark 4.
In a stand mixer with a paddle attachment add the rest of the ingredients and mix on medium speed until combined.
Roll out the dough to line the 9" pie pan, pour in the filling and bake uncovered for an hour or until when the side of the pie pan is tapped the center has a little wobble.
Allow to cool to room temperature before placing in the refrigerator. Chill for at least 3 hours.