Preheat oven to 350. Brush a 9 inch tart pan with melted butter. Sift flour inot a large bowl. Add butter. rub butter into flour until mixture is fine and crumbly. Stir in sugar. Add yolk and water. Mix to soft dough, press into ball. Roll pastry between 2 sheets of plastic wrap, Trim edges, prick pastry evenly with fork, Refrigerate for 20 mnutes. Bake for 35 minutes. Place sugar and flour in small pan. Make a well in the center. Add milk and whisk in gradually. add butter, stir over low heat for 8 minutes, until mixture boils and thickens. Remove from heat, add vanilla and yolk. Whisk until smooth. Spread filling into pie. Place egg whites in small dry bowl. Use electric beaters, Beat until stiff peaks form. Add sugar gradually, until mixture is thick and glossy. Spoon Meringue over filling. Bake for 20 minutes. Serve.