Preheat your oven to 350 degrees F, make sure a rack is in the center of the oven and and grease a 8 x 10 (2.8 qt.) baking dish and line with parchment paper, letting the excess fall over the sides.
Place the 12 tablespoons butter, granulated sugar and brown sugar in an electric stand mixer fitted with the paddle attachment and mix on medium until creamy and well blended, about 4 minutes. Add in the pumpkin and mix for 1 minute more. Periodically scrape down the sides and bottom of the bowl to make sure everything is well blended. With the mixer on low, add the eggs one at a time mixing completely before adding in the next. Add the water and vanilla and run the mixer on low for 1 minute more.
In a medium bowl whisk together the flour, cinnamon, baking powder, baking soda, sea salt, allspice, nutmeg, ginger and cloves. Pour into the stand mixer and mix on low until barely combined and you still see streaks of flour. Take the bowl out of the mixer and gently fold the batter several more times until you see no more streaks. Pour the batter into the prepared baking dish, smoothing the top and gently tapping on the counter several times to release any trapped bubbles.
Bake in the center of the oven for 40-45 minutes. I like to lightly press the center of the cakes to see if it's done…if it springs back it's done. Let cool for 15 minutes in the pan, then use the parchment overhand to pull the cake from the pan and finish cooling on a cooling rack. Once the cake has cooled, place it back in the pan.
In a small saucepan heat the sugar and water, stirring until the sugar has melted. Whisk in the bourbon and pour over the cooled cake.
To prepare the buttercream, place the 8 tablespoons butter in a medium saucepan and melt over medium heat. Once melted, crank up the heat to medium high. Stand by, stirring and watching. Small golden bits will start to settle on the bottom of the pan and it will start to smell delicious and nutty. Once this happens, take it off the heat and pour into a small, heat-safe bowl to cool completely.
In an electric stand mixer fitted with the paddle attachment add the cooled brown butter, bourbon and milk and mix on low until combined.. Add in the powdered sugar and mix on low until fully blended and smooth. Add in the cinnamon, nutmeg and mix until smooth. Spread over the top of the cake…I like to leave a ½-inch gutter around the edge of the cake so that you can see it when looking over the top. But you do you! Enjoy!! **I sprinkled some nutmeg over the top (because I love it), but again, you do you!
Thank you so much for making this Pumpkin Bourbon Cake With Brown Butter Buttercream -- I hope you love it as much as we do!! Please tag me on social @displacedhousewife #displacedhousewife so I can see your gorgeous cakes! Happy October!!