Combine 1/4 cup butter, 1 cup sugar, salt, and egg yolks in a large mixing bowl; beat well. Add lemon juice, orange rind, nutmeg, potatoes, and half-and-half; beat until well blended. Beat egg whites (at room temperature) until stiff peaks form. Fold into sweet potato mixture. Pour filling into pastry shell.
Combine 1/4 cup melted butter, brown sugar, and pecans; mix well. Sprinkle pecan mixture evenly over top of filling. Bake at 425° for 10 minutes. Reduce heat to 350°; bake an additional 30 minutes or until a knife inserted in center comes out clean. Cool before serving.