Heat oven to 400 degrees F.
Mix pineapple, sugar, cornstarch, salt if using, in saucepan. Simmer, stirring, 4 minutes, until very thick. Remove from heat. Stir in margarine and lemon juice. Cool 10 minutes.
For bottom crust, roll out half of dough on well-floured surface into 12-inch round. Fit into 9-inch pie plate. Spoon in cooled filling.
Roll remaining dough into 10-inch round. Cut into 1-inch wide strips. Weave strips in crisscross lattice over filling. Fold lattice strips under edge of bottom crust; crimp.
Bake in 400 degree F oven 25 to 30 minutes, until nicely browned. Let cool completely before serving. Makes 8 servings.