Make Cherry Filling - In a medium saucepan, whisk together 1/3 cup sugar, cherry brandy, and cornstarch. Pour in the cherries and their juices. Bring the mixture to a boil and stirring constantly over medium-high heat.
After about four minutes, once the mixture is thickened, remove from heat. Let the mixture cool to room temperature.
Preheat Oven and Prepare Pan - Preheat the oven to 350 degrees Farenheit. Rub butter on the bottom of the pan, then adds a layer of parchment paper, allowing it to lay two inches over the side. Butter the parchment paper.
Mix Together Hot Water, Cocoa Powder, Sour Cream, and Melted Chocolate - In a medium bowl, whisk together hot water and cocoa powder until smooth. Then, add in the sour cream and melted chocolate.
Mix Together Dry Ingredients - In a different medium bowl, mix together the cake flour, baking soda, and salt.
Beat Butter and Sugar - In a large bowl with an electric mixer, beat the butter and 1 2/3 cups of sugar. Beat on medium speed for about 3-4 minutes and until light and fluffy.
Add in Eggs and Vanilla - Add eggs one by one and beat them well after each addition. Mix in the vanilla extract.
Add Flour Mixture and Chocolate Mixture - With the mixer on low speed, alternate adding the flour mixture and chocolate mixture. Beat until well combined.
Add in Cherries - Fold in 1 1/4 cups of the cherry mixture into the cake batter. Save the remaining cherry mixture for later.
Bake the Cake - Pour the batter into the prepared pan. Bake the cake for 50 minutes, or until a toothpick inserted into the middle comes out clean. Allow some time for the cake to cool on a wire rack.
Make the Frosting - In a small saucepan, heat the gelatin and water over low heat. Stir the mixture constantly for about three minutes until the gelatin is melted.
In a large bowl, use an electric mixer to beat together the heavy whipping cream and remaining sugar on medium speed. Once the soft peaks begin to form, slowly add in the gelatin.
Decorate the Cake - Decorate the cake with the frosting and then cover with the remaining cherry mixture. Slice and serve the cake.