Preheat the oven to 350 degrees F.

Grease and line two 9" cake pans with parchment paper.

In a medium bowl, combine the flour, baking powder, baking soda, salt, and pumpkin spice. Set aside.

In a separate large bowl, whisk together the brown sugar, granulated sugar, and oil.

Then, whisk in the eggs and vanilla, and lastly the pumpkin purée.

Add the dry ingredients to the wet and whisk until fully combined and smooth.

Pour the batter into the prepared pans and smooth out the top.

Bake the cake layers for about 20-25 minutes or until a toothpick inserted comes out clean and the cake starts pulling away from the sides of the pan.

Immediately turn the cakes out onto a wire rack to cool completely.

In the bowl of a stand mixer fitted with a paddle attachment, beat the butter and cream cheese on high speed until smooth.

Slowly add the sifted powdered sugar and mix on low speed until fully combined. Once all of the powdered sugar is added, continue beating on low speed until no more lumps or pockets of air remain and the frosting is smooth.

Use a serrated knife to cut the two cakes in half to get four layers.

Secure the first cake layer on the cake stand with a small amount of frosting on the bottom. Using an offset spatula, spread on an even layer of frosting, then place the second cake layer on top. Repeat with the remaining layers.

Spread an even layer (or crumb coat) of frosting along the top and outside of the cake, then place in the fridge for about 10-15 minutes.

Take the cake out of the fridge and spread a thicker layer of frosting on the cake. Use the remaining frosting to pipe along the top and bottom of the cake, if desired.