To Make the Crust: 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 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.

Preheat oven to 350 degrees F (175 degrees C).

Beat ricotta, yolks, and sugar until lemon colored. Add lemon juice, zest, and vanilla.

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.

Bake at 350 degrees F (175 degrees C) for 45 to 50 minutes. Let pie cool then refrigerate to set; the pie will become creamy and dense. Serve cold.