Place flour in bowl. Add shortening, cutting it in with pastry cutter or two knives until shortening is blended and resembles coarse meal. Sprinkle in ice water and toss to mix. Gently form dough with hands and pat it into disk. Roll dough out on a floured board into a circle larger than the outside rim of a nine-inch pie plate, so there’s an edge to crimp. Lay dough inside pie plate, crimp edge, and refrigerate while preparing filling.
Preheat oven to 350°F. Beat together sweet potatoes, eggs, vanilla, and lemon juice. Combine flour, sugars, spices, and orange zest, and beat into potatoes. The mixture should be uniform. Pour filling in pie crust. Bake in preheated oven for 35 minutes.