Peel the fruits and break them into chunks. Bring the fruits to boil in a saucepan with a few tablespoons of water (to prevent them from sticking to the pan's bottom at first) over medium heat. Let them boil for a few minutes until cooked.
In a small dish add 2 tbsp of fresh water to the gelatin and stir until all the gelatin is wet. Add the gelatin to the fruits right after you turn off the heat under the pan. Stir to incorporate the soft gelatin in the bananas. Add the vanilla extract and stir it in, too.
Pour the mixture into a blender and blend it until it's nice and smooth. Set the mixture aside to cool down.
Meanwhile, the fruits are cooling down, begin whipping the egg whites with the cream of tartar. When they forth a bit add the sugar or the erythritol and keep whisking until the meringue is stiff.
With the mixer still running begin adding the fruit mixture to the meringue, a tablespoon at a time. Keep whipping the mix for a few more minutes. The mixture will grow in volume.
Pour your whipped dessert into the serving bowls and devour right away or stick it in the fridge to harden up and enjoy it within the next 1-3 days!