How to make
Mix the gelatin with the water, leave it for 30 minutes, then heat in a water bath until dissolved. Peel the kiwis, grate them and blend to a puree.
Sweeten the yogurt with the sugar, add the kiwi puree, citric acid and dissolved gelatin. Stir the mixture well.
Cut the peeled banana into round slices and arrange in a nonstick baking dish, pour the yogurt mixture in.
Let the cake sit in the refrigerator for 2 hours. When serving, garnish with the remaining slices of kiwi and grapes, cut in halves.