Preheat oven to 400°.
Combine flour, 1 1/2 tablespoons sweetener, and salt. Cut in shortening until mixture resembles coarse meal. Add ice water and vinegar; toss with a fork until moist. Shape into a ball. Roll into a 14-inch circle on a lightly floured surface. Place dough in a 10-inch pieplate; press against bottom and sides of plate. Flute edges.
Drain cherries, reserving 1 1/4 cups liquid. Set cherries aside. Combine reserved cherry liquid, 1/2 cup sweetener, and cornstarch in a saucepan; stir well. Cook over medium heat until very thick, stirring constantly. Stir in cherries, cinnamon, and almond extract.
Pour mixture into pastry shell. Shield pastry with foil, and bake at 400° for 20 minutes. Reduce heat to 375°; bake, unshielded, 25 to 30 minutes or until hot and bubbly. Serve warm or at room temperature.