The trick to a really crisp bottom is preheating the baking sheet. And make sure you use a rimmed sheet, or else you'll have a juicy mess all over the bottom of the oven.
For the pastry dough:
1 1/2 cups flour
3/4 teaspoon salt
1/4 cup sugar
6 ounces cold butter, cut into pieces
3 tablespoons ice cold water
For the filling:
12 plums, pitted and quartered
1/2 pint blackberries
2 tablespoons butter, cut into pieces
1/4 cup sugar
Place a rimmed baking sheet onto the center rack of the oven. Preheat oven to 400º.
To make the pastry dough, add the flour, salt and sugar to a deep bowl; whisk to combine. Scatter the butter pieces over flour mixture and use a pastry blender, two butter knives or your fingers to cut in the butter (this can alternately be done in a food processor). Sprinkle the cold water over the butter-flour mixture and stir with a fork until the dough forms a rough ball. Wrap in plastic and let rest in the refrigerator for 20 to 30 minutes.
On a lightly floured piece of parchment paper, roll the dough out into a 16-inch circle. Scatter the fruit over the dough, leaving a 4-inch border. Sprinkle the sugar over the fruit and dot with the pieces of remaining butter. Fold the dough border up and over to cover the fruit, forming a crust. Leaving the tart on the parchment paper, place it on the heated baking sheet. Bake 40 to 45 minutes, or until pastry is a deep golden and the fruit is bubbling in the center. Let cool for 10 to 15 minutes. Serve warm or at room temperature.
Serves 6 to 8
Follow the directions for making the blackberry plum tart, except use peaches and raspberries instead.
One unbaked pie tart crust
4 peaches, peeled and sliced
1/2 pint raspberries