Put 1/2 stick butter into a large saucepan. Using a paring knife, scrape the seeds from the vanilla bean into the saucepan and add the pod. Cook over medium heat until the butter is lightly browned, about 2-3 minutes. Add the apples, cider and 1 cup of granulated sugar. Raise the heat to medium-high, and cook, stirring occasionally, for 10 minutes. Reduce the heat to low and cook until apples are golden and translucent and the liquid has evaporated, about 10 minutes. Discard the pod and let cool.

Preheat oven to 350 degrees. Butter two 9-inch round cake pans (or 8-inch if you don't have 9's). Dust with flour and tap out the excess. Set aside. Whisk together the flour, baking powder, baking soda, salt and spices. Reserve 1/4 cup of spiced flour mixture. Set all aside.

Beat remaining 2 sticks of butter, remaining 1 1/2 cups granulated sugar and the brown sugar with a mixer on medium-high until pale and fluffy, about 5 minutes. Reduce speed to medium and add eggs, 1 at a time, beating well after each addition. Reduce to low and alternate the flour and sour cream in 2 batches each. Scrape down the sides of the bowl as needed. Add the remaining 1/4 cup of flour and caramelized apples and fold gently to combine.

Divide batter between the prepared cake pans. Bake until tops are dark golden brown and a toothpick inserted comes out clean, about 40 to 45 minutes. Let cool for 10 minutes on a wire rack. Run a knife around the edges and turn cakes out onto a cooling rack. Cool completely.

In a medium bowl add the brie, cream cheese and butter and beat with a hand mixer until light and fluffy, about 3 minutes. Add the vanilla and mix to combine. Add 3 cups of sifted powdered sugar and mix to combine until light and fluffy. Add more powdered sugar if needed to reach your preferred consistency.

In a small skillet, add the pecans and toast over medium heat. Add the sugar and stir quickly to coat. Turn out onto a piece of parchment paper and let cool completely.

Place one layer of cake on a cake pedestal or plate. Top with 1/2 of the Brie icing and using an offset spatula, spread all the way to the edge. Place in the freezer for 5 to 10 minutes. Remove from the freezer and top with the second layer of cake. Top with the remaining icing and spread evenly over the top. Top with the sugared pecans and serve.