Rose Galletta's Ricotta Pie

1 1/2 pounds ricotta cheese
6 eggs, separated
1/2 cup white sugar
1/4 teaspoon lemon juice
1/4 teaspoon lemon zest
1/2 teaspoon vanilla extract
2 cups all-purpose flour
6 tablespoons white sugar
1 teaspoon baking powder
1/8 teaspoon salt
1/2 cup butter
1/4 cup milk
1 egg
2 tablespoons lemon zest
                   
1. To Make Shell: Combine the flour, 6 tablespoons white
   sugar, baking powder, salt and lemon zest. Cut in the
   butter until the mixture resembles coarse crumbs. Stir
   in the milk and the 1 whole egg. Work dough until it
   forms a ball. Do not knead or over work the dough.
   Generously flour a work surface and roll dough out to fit
   into a 9 inch pie plate. Place dough in a greased pie
   plate. Poke holes in the center with the tines of a fork.
   Do not prebake. 
2. Preheat oven to 350 degrees F. 
3. Beat ricotta, yolks, and sugar until lemon colored. Add
   lemon juice, zest, and vanilla. 
4. Beat whites until stiff, fold into lemon mixture. Pour
   mixture into the prepared shell. Do not over fill the shell,
   it rises slightly when baking. 
5. Bake at 350 degrees F for 45 to 50 mins. Let pie cool then
   refrigerate to set, the pie will become creamy and dense.
   Serve cold.