The filling: Melt the butter in a saucepan and add the apple slices. Drizzle
with lemon juice. Cover and simmer over low heat for 5 minutes.
Transfer apples to a bowl and let cool.
The topping: Combine the flour, sugar and butter in a food processor; process
into pea-size crumbs. Stir 1 tablespoon of the crumbs into the warm apples.
Reserve the rest of the crumbs for topping.
The pastry (yields enough for 2 crusts): Combine the flour, sugar and salt in a
food processor; process just to blend.
Cut the cold butter into 1-inch cubes. Put in the processor and stir to
distribute evenly and coat the cubes with flour. Pulse until the mixture is in
pea-sized pieces.
Drizzle 4 tablespoons ice water and the vinegar over the mixture. Pulse enough
times (about 6) just to combine, but do not let the dough form a blob around the
blade.
When you pinch the dough together (careful of the blade) it should stick
together. If it doesn't, drizzle on the remaining tablespoon of ice water. Pulse
2 or 3 times.
Place a large sheet of plastic wrap on a work surface. Remove the dough from the
processor bowl (it can still be in pieces) and put in the middle of the plastic
wrap. It will look like a mess.
Pull up the sides of the plastic wrap to form the dough into a flat disc.
Refrigerate for 1 hour.
Remove dough from refrigerator and divide it in half. Wrap one of the halves in
plastic wrap and place in a heavy-duty freezer bag. Mark, date and place in the
freezer.
Freezes well for up to 2 months.
Adjust the oven rack in the center of the oven; preheat the oven to 400 degrees.
Place a 14-inch length of parchment paper on a work surface. Dust very lightly
with flour.
Put the dough disc on the parchment and, starting from the center, roll out to a
10-inch circle. As you roll, you'll have to keep sliding a spatula underneath
the dough to keep it from sticking.
Lift the parchment and dough round onto a baking sheet. Mound the cooled apple
filling in the center, leaving a 2-inch border around the perimeter.
Sprinkle the crumb topping over the apples. Fold the edges of the pastry over
the apples. Press the edges a into a free-form circle. You don't have to be
perfect.
Place in the oven and bake for about 30 minutes, or until pastry is golden.
Cut into wedges and serve drizzled with warm dulce de leche. Garnish with
whipped cream.
