Preheat the oven to 325 degrees F, lightly mist two 8 inch round pans with non-stick spray, and line with parchment paper round.
Place the flour, sugar, brown sugar, baking powder, baking soda, salt, cinnamon, nutmeg, and ginger in a large mixing bowl, and whisk together until combined.
Add the butter, and mix on medium-low speed until the mixture resembles damp sand.
Add the eggs, one at a time, allowing each one to fully incorporate before adding the next.
Stir in the pumpkin puree, sour cream, and vanilla, then scrape the bottom and sides of the bowl with a silicone spatula.
Turn the mixer up to medium speed and mix for about 90 seconds, to aerate the batter and develop the cake's structure.
Transfer the batter to the prepared pans and smooth the batter with an offset spatula. Bake for 22 to 27 minutes, or until a toothpick inserted in the thickest part of the cake comes out clean.
Allow the cakes to cool completely in the pans set on a wire cooling rack before decorating.