Preheat oven to 350°F. Prepare three 8 inch round pans with baker's floured spray (or grease and line with parchment rounds).
Mix together all dry ingredients (flour, sugar, baking powder, salt, and spices) in a stand mixer until fully combined.
Mix chunks of room-temperature butter slowly into the dry mix, on a low speed. Continue to mix until no large chunks of butter remain, and the mixture starts to look like crumbs.
Stir in eggs, and mix on low until just incorporated. Mix the pumpkin puree and Brown Sugar Bourbon into the buttermilk and pour the mixture into the dry ingredients in two installments, on a low speed. Add in oil, and mix at a low speed until fully incorporated. Scrape down the sides of the bowl with a spatula, then beat on medium speed for 20-30 seconds, until the mixture becomes smooth.
Divide batter evenly between the prepared cake pans (I find a kitchen scale helpful for this part).
Bake for 34-37 minutes (or until a toothpick comes out clean). Allow cake layers to cool for 10-15 minutes on a wire cooling rack before removing from pans, and cool completely before frosting.
Set in the fridge or freezer to accelerate the cooling process if desired.
Once the layers have fully cooled, they can be leveled and any caramelized bits can be trimmed from the sides / top of the cake using a serrated knife if desired. Be sure the layers are completely cooled or chilled before trimming. If you try to trim the layers while they’re still warm, they will crumble and break. (This is a great time to make your frosting!)