Heat oven to 350°F.
Coat a 9" square cake pan with cooking spray. Dust with 1 teaspoon cocoa. Set aside.
Combine prunes and coffee in a bowl. Set aside to cool.
Combine remaining 1/3 cup cocoa, flours, baking powder, baking soda and salt in a large resealable plastic bag; shake.
Add sugar, applesauce, egg white and 1 teaspoon of the vanilla to coffee-prune mixture. Empty bag into bowl; mix.
Pour into prepared pan. Bake until a toothpick inserted in center of cake comes out clean, 20 to 25 minutes. Cool completely before removing and slicing.
Mix 1 tablespoon water, remaining 1 teaspoon vanilla and gelatin in a small pan. Set aside until gelatin becomes clear, 10 to 15 minutes.
Heat over low heat until gelatin melts. Mix gelatin, sour cream and confectioners' sugar in a bowl. Refrigerate until topping is firm, 10 to 15 minutes. Beat until smooth.
Add a dollop to each slice of torte.