Preheat the oven to 375 degrees. Roast the pumpkin, cut side down, on a slightly oiled baking sheet until completely tender, about 45-60 minutes. Scoop the flesh from the pumpkin and combine in a blender or food processor with the cream, eggs, sugar, oil, cinnamon, salt and vanilla until smooth. Bake in a pre-baked pie crust in a 350 degree oven for about 1 hour, or until the filling is set. Top with freshly whipped cream.