1. Weigh flour. Combine first 4 ingredients in a bowl; cut in shortening with a pastry blender until mixture resembles coarse meal. Make a well in center of flour mixture. Combine 1/4 cup boiling water and melted butter in a bowl. Pour butter mixture into center of well. Gently draw flour mixture into butter mixture until moist clumps form. Press dough into a 4-inch circle; cover. Chill for 30 minutes.
2. Preheat oven to 400°.
3. Unwrap dough; place between 2 sheets of plastic wrap. Roll dough into an 11-inch circle. Remove top sheet of plastic wrap. Fit dough, plastic wrap side up, into a 9-inch round tart pan coated with cooking spray. Remove plastic wrap. Press dough into bottom and up sides of pan; fold excess crust back in and press. Pierce bottom and sides of dough lightly with a fork; freeze 10 minutes. Line bottom of dough with foil; arrange pie weights on foil. Bake at 400° for 18 minutes. Remove foil and pie weights. Bake 15 minutes or until lightly browned. Cool on a wire rack.
4. Combine cranberries, 1/2 cup sugar, 1/4 cup water, and 1/8 teaspoon salt in a medium saucepan. Cook over medium-high heat 10 minutes or until cranberries burst. Combine 1/2 cup sugar, 1/2 cup water, cornstarch, and egg yolks in a small bowl; stir with a whisk until smooth. Gradually add 1 cup hot cranberry mixture to egg mixture, stirring constantly. Return egg mixture to pan. Cook until a thermometer registers 160°, stirring constantly.
5. Place a food mill or fine sieve over a large bowl. Pour cranberry mixture into food mill, and press through. Discard solids. Add 2 tablespoons butter; stir. Spoon into baked crust. Cover and chill.
6. Preheat broiler.
7. Place egg whites and 1/8 teaspoon salt in a large bowl; beat with a mixer at high speed until soft peaks form. Combine 1/2 cup sugar and 1/4 cup water in a small saucepan; bring to a boil. Cook, without stirring, until candy thermometer registers 238°. Gradually pour hot sugar syrup into egg white mixture, beating until stiff peaks form. Spread meringue over cranberry curd.
8. Broil meringue for 30 seconds or until lightly browned.