Preheat oven to 350°F. Grease two 9-inch cake pans with butter and line the bottom of each pan with parchment paper. Grease the parchment paper and set it aside.
In a medium bowl, whisk together the flour, baking powder, baking soda, and salt until combined. Set aside.
With an electric mixer, cream the butter until light and fluffy. Add the sugar in a steady stream, mixing until completely incorporated. Scrape down the sides of the bowl as needed.
With the mixer on low speed, add one egg at a time to the batter, mixing until just incorporated before adding the next egg.
Stir in the vanilla extract and gelatin. Alternately add the buttermilk and dry ingredients to the batter, beginning and ending with the dry ingredients and mixing until just combined.
Divide the batter between the two cake pans and spread evenly. Bake for 30-35 minutes or until a toothpick inserted into the center of each cake comes out clean. Allow cakes to cool in pans for 10 minutes before turning them out onto a cooling rack.
While the cakes are cooling, make the sweetened berries by combining 3 tablespoons of sugar with 2 pounds of strawberries in a medium bowl. Set aside to macerate.
Make the topping by whisking together cold heavy cream, vanilla extract, and 1 tablespoon of sugar until soft peaks form.
Using the handle of a wooden spoon, poke holes all over each cake. Pour half of the macerated berries over each cake making sure to get some of the juices as well. Spread the remaining half of the berries in between the two layers and spread topping over top, sealing edges with a spatula.