Grease and flour the cake pan. Preheat oven to 350 degrees F.
Cream the butter with 1/2 cup of the sugar until light and fluffy. Add another 1/2 cup of sugar and beat until incorporated. Gradually add in the buttermilk, scrape down the sides of the bowl. Add the egg whites in 1 at a time, beating well after each addition.
In a separate bowl stir together the flour and baking powder. Add the flour mix into the batter with the vanilla and mix together until well incorporated.
Pour the batter into the prepared pan and arrange the mango, pineapple, and banana decoratively on the top. Sprinkle with the remaining 2 tablespoons sugar and bake for 45 minutes or until golden brown.
Let the torte cool slightly and slice. Serve each slice warm with a small scoop of vanilla frozen yogurt, 2 caramelized banana slices and 2 tablespoons of raspberry sauce.
Slice the bananas on the diagonal into 24 slices and place on a baking sheet. Sprinkle with the sugar and caramelize under a broiler for 1 to 2 minutes.
Place raspberries, sweetener, and lemon juice in a blender and process until smooth. Strain and set aside.
Yield: 1/2 cup