Make the tart crust (see Judy's Baking Book or any good cookbook).
Preheat the oven to 425 degrees.
Heat the butter or margarine, granulated sugar, and salt in a medium-size skillet over medium heat until the mixture starts to caramelize, about 3 minutes. Add the apples and sauté them just until they have lost their crispness. This will vary considerably depending on the apples.
Spread the apples evenly in the baked tart shell, along with any remaining syrup in the skillet. Paint the edge of the shell with a bit of egg glaze.
Remove the top crust from the refrigerator, peel off the top piece of plastic, and flip the dough over on top of the tart. Peel off the second piece of plastic wrap and use your index finger to press the dough onto the edge of the crust, allowing the excess to drop off. Brush the egg glaze lightly over the top crust.
Cut 3 or 4 slits in the top crust. Bake the tart on the center oven rack until the top is golden brown, 25 to 35 minutes. Use a toothpick to pierce through the tart to make sure the apples are cooked through. Baking time varies with ovens and the type of apple used, so check the tart at 20 minutes and every 5 minutes after that until done.
Remove the tart from the oven and allow it to cool. Sprinkle the tart with confectioner's sugar before serving.
Makes 8 to 10 servings.
Judy Rosenberg is also the author of Rosie's Bakery All-Butter Fresh Cream Sugar-Packed No-Holds-Barred Baking Book and Rosie's Bakery Chocolate-Packed Jam-Filled Butter-Rich No-Holds-Barred Cookie Book.