Combine the flour, salt and sugar in a food processor fitted with a metal blade. Pulse several times to mix ingredients.
Add the butter and shortening and pulse 10-15 times until the mixture is the texture of coarse sand.
Add the vodka and pulse several times. With the processor running, add the water one tablespoon at a time until the dough just comes together into a ball, but is not wet. Do not process too long or the pastry will be tough.
Dump the dough out on a generously floured surface and work into the shape of a disc.
Wrap in wax or parchment paper and refrigerate 30 minutes.
Preheat oven to 375 degree F and adjust rack to the middle of the oven.
Roll the dough out on a generously floured work surface until it is about 1 1/2-inches bigger on all sides of a 9-inch tart pan with a removable bottom. Gently transfer and ease into the dough into the tart pan trimming the excess dough.
Press a piece of foil on top of the dough and refrigerate 15 minutes. The foil will prevent the dough from shrinking while baking. Bake crust 10 minutes.
Gently remove the foil, prick bottom and sides with a fork in several places and continue baking 2-4 minutes or until the crust is golden brown. Remove from oven and cool completely. Increase the oven to 425 degree F.
For the filling:
Place the mascarpone and cream in a stand mixer fitted with a paddle attachment, a hand mixer may also be used.
Mix on medium speed until combined. Scrape down sides and add the Lemon Curd and sugar. Mix on medium speed until thick and creamy.
Spread filling over tart crust.
For the meringue:
Make sure the mixing bowl is clean and free of any oil or grease.
Whisk the egg whites and cream of tartar until soft peaks form.
Add the sugar, vanilla and salt and continue to whisk on high speed until stiff peaks form, but the egg mixture is still smooth.
Pipe or spread meringue over lemon filling making sure the meringue touches the edges of the crust to prevent shrinking.
Bake for 4-6 minutes until the meringue is golden brown. Remove from oven and cool.
Refrigerate at least 2 hours or up to overnight before serving.