In a food processor, combine the flour, salt and sugar. Add the butter and pulse a few times, then add the shortening and pulse a few more times but do not over mix. While pulsing, drizzle in the cold water. Dump the dough onto a work surface. It will still be very loose. Work the dough together with your hands into a flat disc. Wrap with plastic and place in the refrigerator to rest for at least 1 hour.Unwrap and roll the pastry out to a 12 inch circle. Use a bench scraper to roll the dough around your rolling pin, then unroll it over a 9 inch pie pan. Gently work the dough into bottom of the pan and up the sides. Tuck excess pastry at the edge of the pan into itself to make a sort of 'log' around the top of the crust, then use your index finger on one hand to push dough through the index and middle finger of your other hand to make a fluted edge. Place the prepared pastry into the freezer for 30 minutes. Turn the oven on to 375 degrees. Remove the pastry from the freezer and place it onto a sheet pan. Line the inside of the pastry with parchment and fill with dry beans. Bake dough for 20 minutes. Remove from the oven and carefully remove the parchment and beans. Use the tines of a fork to 'dock' the bottom of the crust. Place in the oven and bake for an additional 15 minutes.Remove the pan from the oven and turn the temperature down to 350 degrees.
Make the meringue.
Pour the sugar into a food processor and turn it to high for about 30 second to make superfine sugar that will dissolve better into the meringuePour the egg whites into the bowl of a stand mixer with a whisk attachment or in a large bowl with a hand mixer. Whisk on medium high speed until they become foamy. Add the cream of tartar and whisk until the whites begin to approach soft peaks, which will happen after a couple more minutes of whisking. You will know because the bubbles will become tighter and the meringue will appear cloud-like. With the mixer still running, begin adding the sugar a spoonful at a time until it is all in, then continue to whisk until it reaches stiff peaks. When you lift the whisk attachment out of the bowl and turn it upright, the meringue that is adhered to the tip will form a peak that does not fall back onto itself.Set the meringue aside while you make the filling
Make the orange filling.
In a medium saucepan on medium heat, whisk together the lemon and orange zests and juices, sugar, vanilla, salt, cornstarch and water. It will look cloudy at first. After about 5 minutes, it will begin to thicken up. Whisk it for a couple minutes until it is thick and glossy. In a separate bowl, whisk the egg yolks. Drop a few spoonfuls of the hot orange mixture into the yolks and whisk to combine. This will cook the yolks without scrambling them. Pour the tempered yolks into the saucepan with the remaining custard and stir to combine. Turn off the heat.
Assemble and bake the pie.
While the crust is blind baking, make the meringue and the filling so everything comes together all at once. Filling needs to be very hot when you top it with the meringue so the bottom layer of meringue begins cooking instantly, which will help prevent weeping. Pour the hot orange filling into the par-baked crust and use a rubber spatula to spread it evenly.Immediately top with the meringue and use a rubber spatula to create decorative peaks. Place the pie in the oven and bake for 20 minutes. Remove from the oven and allow to cool completely at room temperature before chilling.