To Make Filling: In a medium bowl blend together cornstarch, sugar and salt, then stir in egg yolks and 1/2 cup of pineapple juice. Scald milk and cool slightly; whisk cornstarch mixture into scalded milk and bring to a boil over low heat until mixture thickens. Allow to cool for a short amount of time, then stir in 3/4 cup of the drained pineapple and vanilla to the cooked mixture and set aside to cool.
To Make Dough: In a large bowl sift together flour, salt and baking powder; cut in margarine. In a small bowl, slightly beat milk and eggs together. Combine egg mixture with dry ingredients; mix together until dough is formed.
To Make Crust: Divide dough into two parts. Take one part and roll between sheets of floured wax paper; rolled dough should fit a jelly roll pan allowing for slight overhang on edges. Roll remaining half in the same fashion.
Transfer one of the rolled dough halves to pan and spread with cooled filling. Place other portion of rolled dough on top of the filling and crimp edges of dough layers together.
Bake at 350 degrees F (175 degrees C) for 40 minutes or until golden brown. Let cool. If desired, frost with confectioners' icing.