Italian jam tart

This is a very simple yet very good traditional Italian jam tart, made with pastafrolla--Italian-style shortpastry. The original post is from my blog

From the original recipe by Pellegrino Artusi
In: La Scienza in Cucina e l’Arte di Mangiar Bene” , 1891–Italy

Ingredients

2 cups (250 g) AP flour, unbleached
1/2 cup (125 g) unsalted butter, diced
1/2 cup (110 g) sugar
1 medium egg
1 yolk
1 cup (260 g) fruit jam (such as apricot, plum, or sour cherry)

If the granulated sugar is coarse, it is preferable to process it briefly in a food processor or coffee grinder. Mix flour and sugar, then work the butter in with the tip of your fingers until the mixture resembles wet sand. Add the egg and yolk and work briefly until the dough just holds together.
It is important not to overwork the dough (do not knead it) or it will harden when baked.
A food processor works perfectly to make the dough: start by placing flour and sugar in the work bowl, process for a few seconds to mix, then add the butter and pulse a few times until the mixture looks like wet sand. Add the egg and yolk and process a few seconds more until the dough forms. Do not overprocess.

Wrap the dough in wax paper and let it rest in a cool place for at least 30 minutes.

On a lightly floured board roll 2/3 of the pastry dough to a 1/8-in (3 mm) thickness, and line with it the bottom and sides of a 9-in (23 cm) tart pan with scalloped edges and a removable bottom. The sides should be lined with a slightly thicker layer of pastry than the bottom, about 1/4-in (0.5 cm). Fold back in the dough that is hanging over the sides to make a thicker lining along the sides. Cut of excess. Prick the pastry bottom with the tines of a fork in a few places, then spread with the jam. Do not use a deep tart mold.

Roll the remaining pastry on a lightly floured board slightly thicker than 1/8-in (3 mm), then with a sharp knife or pastry cutter cut it in strips 1/4-inch (0.5 cm) wide and make a lattice on top of the jam layer. There might be some leftover pastry. I usually make a few cookies with it, or tartlets.

You can see how the lattice should look here.

Preheat the oven to 400°F (200°C) and bake the tart until golden, about 25 minutes. Unmold the tart as soon as it is ready and let it cool on a rack. If left in the pan it will turn irremediably soggy. It is great freshly baked but it definitely improves after a day or two, if kept in a closed container.

A note on the fruit jam: select a jam that is relatively low in sugar, 38% to 40% content of sugar is best; jams that contain a higher percentage of sugar tend to be adversely affected by the baking temperatures, turning sticky and ruining the final result.