To prepare crust, combine the first 5 ingredients in a food processor; process until finely ground. With processor on, drizzle 3 tablespoons melted butter through food chute, and process until blended. Press crumb mixture into the bottom and up sides of a 9-inch metal tart pan. Bake at 400° for 10 minutes or until toasted. Cool on a wire rack.
To prepare filling, combine 1/2 cup granulated sugar, cornstarch, and dash of salt in a medium heavy saucepan, stirring with a whisk. Stir in lemon juice and egg yolks; bring to a boil over medium heat, stirring constantly with a whisk. Reduce heat, and simmer for 1 minute or until slightly thick, stirring constantly. Remove from heat; add 2 tablespoons butter and rind, stirring gently until butter melts. Spoon the mixture into a medium bowl; cool slightly. Place plastic wrap directly over surface of lemon curd, and chill at least 4 hours or overnight (mixture will thicken as it cools).
Spoon curd evenly into prepared crust. Place 3 egg whites and 1/8 teaspoon salt in a large bowl, and beat with a mixer at high speed until soft peaks form. Combine 1/4 cup granulated sugar and 1/4 cup water in a saucepan; bring to a boil. Cook, without stirring, until a thermometer registers 238°. Pour hot syrup in a thin stream over egg whites, beating until stiff peaks form. Spread meringue over tart. Broil 30 seconds or until lightly browned.