Dough
1 cup all-purpose flour
3 tablespoons packed light brown sugar
1/2 cup cold unsalted butter, cut into 8 pieces

Center a rack in the oven and preheat the oven to 350 degrees F. Set aside a 9-inch square baking pan.

Place flour and brown sugar in a food processor and pulse 3 to 4 times, just to mix. Scatter the butter over the mixture. Pulse several times and then process for about 30 seconds, or until the dough cleans the sides of the bowl and forms curds. Press the dough into the baking pan and bake for 15 to 18 minutes, or until the crust firms and starts to take on color.

Orange Custard
1/2 cup granulated sugar
2 tablespoons all-purpose flour
1/4 teaspoon baking powder
1/3 cup frozen orange concentrate, thawed
2 large eggs
1 1/2 teaspoons Grand Marnier (orange liqueur)
1 1/2 teaspoons fresh lemon juice
Grated zest of 2 oranges

While the crust is baking, wipe out the bowl of the processor (not necessary to wash it) and put in all the custard ingredients. Just before the crust is ready, process the ingredients for 1 minute, stopping once to scrape down the sides of the bowl.

When the crust is ready, remove the pan from the oven, pour the custard over, and tilt the pan to smooth the top. Return the pan to the oven and bake for about 15 minutes, until golden and set. Place the pan on a rack to cool to room temperature.

When the pastry is cool, cut into bars. Just before serving, dust with confectioners' sugar.

Lime Custard Bars
Replace orange concentrate with freshly squeezed lime juice and the grated orange zest with lime zest.