Preheat oven to 350°.
To prepare crust, lightly spoon flour into a dry measuring cup, and level with a knife. Combine 1/4 cup flour, ice water, and lemon juice, stirring with a whisk until well blended to form a slurry. Combine remaining 3/4 cup flour, pecans, powdered sugar, and 1/4 teaspoon salt in a large bowl; cut in shortening with a pastry blender or 2 knives until mixture resembles coarse meal. Add slurry; toss with a fork until flour mixture is moist.
Gently press mixture into a 4-inch circle on 2 sheets of overlapping heavy-duty plastic wrap; cover with 2 additional sheets of overlapping plastic wrap. Roll dough, still covered, into a 12-inch circle. Freeze dough 10 minutes or until plastic wrap can easily be removed.
Remove dough from the freezer. Remove top 2 sheets of plastic wrap; let dough stand 1 minute or until pliable. Fit dough, plastic wrap side up, into a 9-inch pie plate coated with cooking spray, allowing the dough to extend over edge. Remove remaining plastic wrap. Press dough into bottom and up sides of pie plate. Fold edges under, and flute. Place in freezer until ready to fill.
To prepare filling, combine sour cream and remaining ingredients, stirring with a whisk until well blended. Pour filling into prepared crust. Bake at 350° for 45 minutes or until a knife inserted in center comes out clean; cool on a wire rack.