How to Make It
In a food processor, combine the flour, sugar, salt and lemon zest; pulse to mix. Add the butter and pulse until it is in pea-size pieces. Transfer the dough to a lightly floured surface and drizzle on 1/4 cup of the ice water; add more if the dough seems dry. Knead briefly to blend. Pat the dough into a disk, wrap in plastic and refrigerate until chilled, at least 1 hour.
Preheat the oven to 425°. On a lightly floured surface, roll the dough into a 15-inch round. Fit the dough into an 11-inch tart pan with a removable bottom; without stretching the dough, press it into the side. Trim the overhang to 1/2 inch and fold it in to reinforce the side.
Line the shell with foil and fill with pie weights or dried beans. Set the pan on a baking sheet and bake for about 25 minutes, or until the side of the pastry is lightly colored. Remove the weights and foil and bake for about 5 minutes, or until the base of the shell is golden. Transfer to a rack to cool. Reduce the oven temperature to 400°.
In a large bowl, using an electric mixer, beat the eggs with the brown sugar until light, about 2 minutes. Add the pumpkin puree, cream, fresh ginger, 1 1/2 tablespoons of the lemon juice, 1 1/2 teaspoons of the cinnamon, the salt, vanilla, ground ginger, pepper and allspice. Beat until thoroughly blended.
In a bowl, toss the apples with the granulated sugar, the butter, and the remaining 1/2 tablespoon of lemon juice and 1/2 teaspoon of cinnamon.
Pour the pumpkin custard into the cooled tart shell. Starting at the outside, overlap the apple slices in concentric circles over the pumpkin filling. Bake for about 1 hour, or until the apples are tender and golden and the custard is set in the center. Let cool completely, then sprinkle with the amaretti crumbs.