1for the shell:
Put the flour and salt and sugar into the food processor. Give it a whirl to mix well. Add the butter and shortening and blizt in pulses until the mixture looks like coarse cornmeal. Take lid off and drizzle the water on the mixture, then pulse several times - but don't overdo it, it should still look like a bunch of crumbs. Dump the mixture into a bowl and squinch it together till it forms a solid mass. Again, don't overdo it, as you don't want to melt the butter. Them place the dough onto a piece of plastic wrap, fold in the corners of the wrap, and smush the dough into a flat disc. You want the plastic wrap to be firmly wrapped around the dough. Place in the refrigerator for 15 minutes.
Preheat the over to 350 degrees.
Roll out the pastry thinly on waxed paper, and place carefully into a 7 or 8 inch tart pan. Push down gently on the sides to make sure the dough is all the way in. I prefer the 7 inch, but not everyone can find such a thing. Using the rolling pin, remove the excess dough.
2for the filling:
Put all the ingredients into a bowl and mix thoroughly.
Pour into the shell and bake for about 22 minutes.
3for the topping:
Whip cream and sugar and vanilla until nice and stiff, but don't let it turn into butter. Apply evenly, or however you like, to the chilled tart.
4Note: You can mostly use a shallow pie plate for this also. I used a metal tart pan with a removable bottom, which came from England. I love that pan!
Also, you can use two lemons, or two limes, or a lemon and an orange, or what ever. You just need it to be no more than a 1/2 cup liquid.