Preheat the oven to 350ºF.

In a food processor, combine the flour and powdered sugar.  Pulse a few times to combine.  Add the butter and continue to pulse until the mixture looks sandy and the butter is fully incorporated into the flour and sugar.

Rinse the food processor and then combine the eggs, lemon juice, granulated sugar, lemon zest and orange zest.  Process on high until smooth.  Add the butter and blend again on high until smooth.  Set aside.

Place an 11-inch tart pan on a baking sheet.  Pour the crust mixture into the pan.  Press the mixture firmly and evenly into the bottom and up the sides of the pan.

Pour the filing into the crust, then transfer the tart into the oven.  Bake until the center is almost set, 30-35 minutes.

Cool the tart completely.  When ready to serve, sprinkle powdered sugar over the top, add your favourite coulis topping (we happened to have raspberries left over) and cut into slices.