For pastry dough
2 cups all-purpose flour
1 stick (1/2 cup) cold unsalted butter, cut into bits
1 teaspoon salt
4 to 8 tablespoons ice water
raw rice for weighting shell

For filling
1 pound onions (about 2 large), chopped
2 tablespoons lard (need a substitute here)
1 large egg
1/2 cup heavy cream
a pinch freshly grated nutmeg

In a bowl with a pastry blender or with a food processor blend or pulse together flour, butter, and salt until mixture resembles meal. Add 4 tablespoons ice water and toss or pulse until water is incorporated. If necessary add enough remaining ice water to form a dough and form into a disk. Lightly dust dough with flour and chill, wrapped in wax paper, 1 hour.

On a lightly floured surface roll out dough 1/8 inch thick and fit into a 9 1/2 inch round tart pan with a removable fluted rim. Prick bottom of shell lightly with a fork and chill 30 minutes. Line shell with foil and fill with rice. Bake shell in lower third of oven for 10 minutes. Remove rice and foil and bake shell until pale golden, 5 to 10 minutes more. Let shell cool in pan on rack.

Make filling:
In a large heavy skillet cook onions in lard over moderately high heat, stirring, until very soft and golden, about 15 minutes. Transfer onions to a bowl to cool. In a small bowl whisk together remaining filling ingredients and salt and pepper to taste and whisk in onions.

Pour filling into prepared shell and bake in middle of oven until filling is set and top is lightly browned, 25 to 30 minutes.