NOTE: It is SUPER IMPORTANT that all the room temperature ingredients listed above are room temperature and not cold so that the ingredients mix and incorporate correctly.
Heat oven to 335º F/168º C — 350º F/177º C. I tend to use lower setting to prevent my cakes from getting too dark on the outside before the inside is done baking.
Combine your flour, baking soda, baking powder, spices and salt in a bowl and whisk together to combine. Set aside.
In the bowl of a stand mixer, add your eggs, sugar, brown sugar and vanilla. Mix on low with the paddle attachment. You can also do this by hand with a whisk if you don't have a mixer.
Mix until smooth
Add in your pumpkin puree, oil, melted butter and buttermilk and mix until smooth
Add in your dry ingredients one cup at a time until all your dry ingredients are incorporated and your batter is smooth. Do not over-mix.
Pour batter into 8"x2" tall prepared cake pans. Bake the cakes for 40-50 minutes until the center of the cake is set. Let cakes cool ten minutes and turn out onto a cake rack to fully cool before frosting.
Cream the softened butter with the paddle attachment until smooth. Add in your softened cream cheese and continue creaming on low until fully incorporated and smooth.
Slowly add in powdered sugar one cup at a time, letting fully incorporate before adding the next cup. Add in vanilla and salt. Mix at low for 5-6 minutes until smooth.
For a whiter buttercream, add white food coloring. Store leftover buttercream in the fridge for up to a week or freeze up to 6 months.
This buttercream cannot be left out for more than 4 hours.