Preheat your oven to 325 degrees. Spray a 9×13 metal pan on the bottom, line with parchment paper, and spray again. If you need to use metal binder clips to hold down the sides, remember to use metal, not plastic. Set aside

In a medium bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside.

In the bowl of a stand mixer fitted with the paddle attachment, cream the butter, and sugar on medium speed until fluffy and smooth, about 3 minutes.

With a rubber spatula, scrape the bottom and sides of the bowl. Add the eggs, one at a time, on medium speed, beating for 20 seconds after each addition. Stir in the vanilla extract on low.

In a medium size bowl, mix together the sour cream, buttermilk and vegetable oil.

Pour the batter into the prepared baking pan and spread it out evenly.

Bake for about 38-40 minutes, or until a toothpick inserted into the center comes out clean.

Remove from the oven and allow the cake to cool completely in the pan on a wire rack. Once cooled, use the handle of a wooden spoon to poke about 20 holes across the cake, about three-quarters of the way through the depth of the cake.

In a medium bowl, beat the heavy cream until stiff peaks form. Set aside.

In a separate large bowl, beat the cream cheese and butter together until smooth and creamy.

Add the powdered sugar, vanilla extract, and salt, and beat until smooth.

With a rubber spatula, gently fold in the whipped cream until well combined.