Pulse flour, 1/4 cup superfine sugar, and salt in a food processor 2 or 3 times or until blended.
Add butter; pulse 15 times or until mixture is crumbly. With processor running, add 1/4 cup ice water through food chute. Process 10 seconds or just until blended.
Turn dough out onto a sheet of aluminum foil; shape into a 7-inch round. Cover tightly, and chill at least 1 hour or up to 2 days.
Place pumpkin halves, cut side down, in a large, shallow pan.
Bake at 500 for 20 to 25 minutes or until tender.
Remove from oven, and cool to touch.
Scoop out pulp, reserving 6 cups.
Melt 1/4 cup butter in a heavy skillet; add 2 cups sugar, and cook over low heat, stirring constantly, until sugar melts and turns a deep-golden color. Carefully stir in pumpkin pulp (mixture will lump but become smooth with further cooking); cook, stirring constantly, until mixture is smooth. Spoon mixture into a bowl; chill 1 hour or until thoroughly chilled.
Roll dough into an 18-by-15-inch oval on a floured surface; carefully transfer to a baking sheet (dough is very tender). Spoon pumpkin mixture over dough, leaving a 2-inch border. Gently lift border, and fold over filling, pleating dough as necessary.
Bake at 450 for 18 to 22 minutes or until crust is golden.
Sprinkle warm tart with powdered sugar.
Serve with Caramel Sauce, Nanci Courtney's Crem Anglaise, and whipped cream.
