Tapioca: beat egg white in medium bowl with an electric mixer on high speed until foamy. gradually add 3 tbsp. sugar, beating until soft peaks form. mix tapioca, remaining sugar, milk and egg yolk in medium saucepan and let stand for 5 minutes. cook on medium heat, stirring constantly, until mixture comes to a full boil then remove from heat and stir in egg white mixture and extract until well blended. cool 20 minutes before adding topping.
Topping: beat cream and sugar in a chilled medium sized bowl until soft peaks form, add zest and continue beating until stiff peaks form. evenly distribute over tapioca cream and sprinkle with extra lemon zest for a garnish.