Mix sugar, cornstarch, salt, and grated orange peel in top of double boiler. Add orange juice and cook over boiling water, stirring constantly, until thickened, about 15 minutes. Stir in beaten egg yolks and cook another 2 minutes. Remove from heat; add butter and lemon juice. Cool filling slightly . Pour orange filling into a baked 9-inch pastry shell. Beat egg whites until frothy; gradually beat in sugar. Continue beating until stiff peaks form. Cover with meringue all the way to edges. Bake at 350° for about 15 minutes, or until the meringue is nicely browned.
For orange pastry:
Sift together dry ingredients; add orange peel. Cut in shortening until particles are the size of small peas. Add orange juice a little at a time, mixing lightly with a fork, using just enough to hold dough together. Do not overmix. Wrap in waxed paper and refrigerate until thoroughly chilled. Roll pastry out on a lightly floured surface. Fit into a 9-inch pie plate; prick bottom and sides then trim edges and crimp. Or, to help pie keep its shape, use pie weights or fit a second pie plate over the crust to hold in shape. Bake at 450° for 15 minutes, or until lightly browned.