Put the pumpkin in a pot and sprinkle 1.5–2 cups of sugar on it. If you are going to cook it immediately, add half a cup of water and cook over low heat until the pumpkin is very soft. Then mash it with a fork and let it cool.
For the dough, put the flour in a kneading bowl and make a pond in the center. Put the butter and powdered sugar in the center, then knead a soft dough starting from the middle and taking the flour in from the sides. (If you want, you can separate a small piece of dough and make a small decoration on it.) Wrap the dough in cling film and refrigerate for 30 minutes.
Roll out the dough on a lightly floured surface with the help of a rolling pin to the size of your tart mold and spread it on the mold, which you have greased with butter on all sides, with the help of a rolling pin starting from the middle. With your hands, make sure that the dough takes the shape of the tart mold. Press the side edges well, and neatly cut the excess dough from the sides of the mold. Poke a lot of holes with a fork so that the bottom of the dough does not rise while baking. (Or you can put baking paper the size of the bottom of the dough on it and put dried legumes on it.)
Bake the tart dough in a preheated oven at 175 degrees for about 10 minutes.
For the filling, put 3 tablespoons of milk cream, 1 egg, and 1 tablespoon of starch into the pureed pumpkin and mix well with a spoon.
Spread the pumpkin mixture into the tart you baked, and bake it again in the oven at 175 degrees until it turns pink.
Remove it from the oven and let it cool. (I recommend keeping the tart covered in the fridge for one night.)