Combine sugar, salt, cornstarch and lemon rind in sauce pan. Add boiling water, stir to blend well. Cook slowly for about 7 minutes, stirring constantly. Color will become transparent.
Beat egg yolks, then add slowly to hot filling. Cook 5 minutes. Cool slightly and pour into baked pastry shell.
Meringue: Oven temp 325F for 15-20 minutes. Add salt to egg whites and beat until foamy, then add baking powder. Beat until stiff, adding sugar gradually by spoonfuls beating well after each addition.
Add flavoring. Continue beating until mixture piles up fluffy and sugar is well blended and dissolved. Spread meringue on pie, bringing it out to the pastry shell. Spread in careless strokes, leaving surface irregular. Bake as directed until a golden brown.