Invert cake onto serving plate. Cut 1-inch off across the top of cake. Set aside. With a serrated knife, hollow out center of cake leaving a 1-inch border.
In the meantime, warm the grape juice in the microwave for 1 minute. Pour over gelatin mix and combine with juice as you would water. Mix thoroughly and add in peaches and ricotta cheese.
Chill in refrigerator for about 30 minutes.
In a separate bowl, combine non-dairy topping with rum extract and whisk thoroughly. Fill the center of cake with peach ricotta gelatin mix. Return top of cake. Frost cake on top and sides with non-dairy topping and rum extract mixture, completely coating cake.
Chill for 1 hour before serving. Garnish with peach slices.