Combine milk, egg yolks, butter, lemon rind, vanilla, and salt in a medium sauce pan; mix well. Place over medium heat and cook, stirring constantly, until thoroughly heated (mixture will not thicken). Remove from heat.
Combine cracker crumbs and 1/2 cup sugar; fold in to milk mixture. Spoon mixture into six 6- ounce lightly greased custard cups. Place cups in a 13- x 9- x 2 - inch baking pan; add hot water to a depth of 1 inch. Bake at 325° for 35 minutes or until a knife inserted in center comes out clean. Remove from oven, and set aside to cool slightly.
Slightly soften jelly in a small saucepan over low heat. Spread jelly over top of each individual pudding.
Beat egg whites (at room temperature) until foamy. Add remaining sugar, 1 tablespoon at a time, beating until soft peaks form. Fill a pastry bag with meringue; pipe onto center of each pudding.
Bake at 425° for 6 minutes or until meringue is lightly browned. Serve immediately.