Heat your oven to 350 degrees F. Cut two 12-inch lengths of parchment paper and trim each to fit the 8-inch width of an 8×8-inch square baking pan. Press it into the bottom and sides of your pan in one direction, then use the second sheet to line the rest of the pan, perpendicular to the first sheet.

Make the crust: Combine the flour, salt and sugar in the bowl of a food processor. Cut the butter into chunks, and add it to the bowl, then run the machine until the mixture forms large clumps. Transfer the dough clumps to your prepared baking pan and press it evenly across the bottom and ¼-inch up the sides. Bake for 15 minutes, until very pale golden. Transfer to a cooling rack in your freezer for 10 to 15 minutes while you prepare the filling.

Make the filling: In your food processor bowl, grind your pistachios, sugar, flour and salt together until the nuts are powdery. Cut the butter into chunks and add it to the machine. Run the machine until no buttery bits are visible. Add any flavorings and egg, blending until just combined.

Spread filling over mostly cooled crust. Cut apricots in half and remove pits. Arrange the apricot halves in the filling.

Bake the bars for 60 minutes, or until they are golden and a toothpick inserted into the pistachio portion comes out batter-free. Let cool completely in pan.

To finish, you can warm the jam in a small saucepan until it thins, and brush this mixture over the top of the cooled tart, or dust with powdered sugar.

Cut bars into squares and keep leftover bars chilled.