Preheat the oven to 350 degrees. Add 1 cup (227g) butter to a skillet over medium heat. Melt until foamy and brown bits appear on the bottom of the pan, stirring constantly. Once browned, remove from heat and place in a heat safe container. Place in the refrigerator to solidify.
Combine the wet ingredients in a large bowl - pumpkin puree, brown sugar, sugar, maple syrup, eggs, vegetable oil, and vanilla extract. Whisk together for 3 minutes. In a separate medium bowl, combine the dry ingredients - all purpose flour, cinnamon, nutmeg, ground ginger, allspice, ground cloves, baking powder, baking soda, and kosher salt. Whisk until combined.
In a separate medium bowl, combine the dry ingredients - all purpose flour, cinnamon, nutmeg, ground ginger, allspice, ground cloves, baking powder, baking soda, and kosher salt. Whisk until combined.
fold the flour mixture into the wet ingredients and mix until just combined.
Spray three 8-inch cake pans with nonstick baking spray or line with parchment paper. Divide batter equally among the prepared pans and bake for 25-30 minutes, until a toothpick comes out clean. Allow the cakes to cool in the pan for 10 minutes, then turn over onto a wire rack to cool completely.
While the cake bakes, begin making the pumpkin butter filling. Combine pumpkin puree, maple syrup, and pumpkin spice in a small saucepan over medium heat, stirring constantly. Once the mixture is warmed throughout, reduce to low heat and simmer for 15-20 minutes, until the pumpkin mixture has deepened in color and thickened.
Remove from heat and add the butter and stir until the butter is melted. Set aside to cool.
Now make the buttercream. Remove the cooled brown butter from the refrigerator. It should be the texture of softened butter. Place in the bowl of a stand mixer fitted with the paddle attachment on low speed. Beat for 3 minutes, then add cream cheese and continue to beat together for one minute. Add the powdered sugar and meringue powder and a pinch of salt. Continue to mix on low speed, gradually increasing to medium-high speed. Once the sugar is fully incorporated, add the heavy cream and vanilla extract and mix until combined.
Time to assemble the cake layers! Add browned butter buttercream to a piping bag. Place the first cake on a plate or cake stand, then pipe a ring of buttercream around the perimeter of the cake. Add about a ½ cup of pumpkin butter to the middle of the cake and spread around the cake inside of the buttercream ring. Repeat with the second layer and add the third layer on top. Finish with frosting the outside of the cake with the remaining frosting.