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Pumpkin Walnut Cake with Coffee Buttercream

Your new favorite fall cake has arrived this September! Soft and moist pumpkin spice cake is swirled with walnut espresso brown sugar, and topped with a heavenly espresso buttercream. Butter, vegetable oil, and apple cider keep this cake moist and flavorful while the espresso and walnuts bring out the cozy flavors of pumpkin and autumnal spices.
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Prep Time 1 hour 30 minutes
Cook Time 20 minutes
Total Time 3 hours
Servings: 20 slices
Ingredients Method

Ingredients
  

Coffee Walnut Swirl
  • ½ cup raw walnuts
  • ½ cup brown sugar
  • 1 teaspoon espresso powder
  • 2 Tablespoons all purpose flour
  • ¼ cup salted butter melted
Pumpkin Cake
  • 2½ cups all purpose flour
  • 2 teaspoons baking powder
  • 1 teaspoon baking soda
  • 1 ½ teaspoon ground cinnamon
  • 2 teaspoons pumpkin pie spice
  • 1 teaspoon salt
  • ¾ cup vegetable oil
  • ¼ cup salted butter melted
  • 4 large eggs divided, at room temperature
  • 1 15 ounce can pumpkin puree
  • 1 cup brown sugar
  • ½ cup granulated sugar
  • ¼ cup apple cider
  • 1 teaspoon vanilla extract
  • 1 teaspoon apple cider vinegar
Coffee Buttercream
  • 1 ½ cups unsalted butter
  • 1 Tablespoon +1 teaspoon instant espresso powder
  • 1 Tablespoon boiling water
  • 3 ½ cups confectioners sugar
  • 1 teaspoon vanilla extract
  • a pinch of salt
  • ⅓ cup caramelized walnuts chopped

Method
 

Start by making the walnut swirl
  1. In a food processor, pulse the walnuts until they resemble a meal a little coarser than almond flour. Pour into a bowl and toss with the brown sugar, espresso, flour, and melted butter. Set aside until ready to use in the cake.
Make the cake
  1. Preheat the oven to 350℉. Grease two round 8 inch cake pans with butter, line with parchment paper rounds, and then grease the parchment paper. Set aside.
  2. In a large bowl, whisk together the flour, baking powder, baking soda, cinnamon, pumpkin pie spice, and salt. Set aside. In a medium sized mixing bowl, whisk together the vegetable oil, melted butter, egg yolks (we'll use the whites in a moment) , pumpkin puree, brown sugar, white sugar, apple cider, vanilla extract, and apple cider vinegar until smooth. Pour the wet ingredients into the dry ingredients and whisk until smooth.
  3. In a large bowl using a hand or stand mixer fitted with a whisk attachment (or by hand), whip the egg whites on medium high speed to stiff peaks. Fold the egg whites into the batter, trying not to deflate them as much as you can (they will deflate a little though). Divide the batter evenly among the previously prepared pans. Sprinkle the walnut mixture evenly on top of each cake, and use a spatula to swirl it in, folding it into the batter a little.
  4. Bake the cakes for 20-25 minutes, or until they are pulling away from the sides of the pan and an inserted toothpick comes out clean. Let the cakes cool entirely in the pans before frosting.
Make the espresso frosting
  1. In a large mixing bowl using a hand or stand mixer fitted with a whisk attachment, beat the butter on medium speed until creamy, about 1 minute. In a small bowl, whisk together the espresso powder and boiling water .Add it to the butter along with the confectioners sugar, vanilla extract, and salt. Mix on low speed for 30 seconds, before turning up to high speed and mixing for 1-2 minutes or until combined and fluffy.
Assemble
  1. Remove the cakes from the cake pans. If desired, slice a thin layer off of the tops to create an even surface. If you do this, make sure it is a very thin layer or else you may lose a lot of that walnut swirl. Place one layer on a cake stand and spread a layer of the coffee buttercream on top. Sprinkle on the caramelized walnuts, and top with the second cake layer. Spread layer of frosting on top of the cake. If desired, dye some of the frosting orange and pipe pumpkins onto the cake. I used piping tip Wilton 4B to do mine, and then I topped each pumpkin with mini chocolate chips as stems.
  2. Slice, serve, and enjoy! Cake stays fresh stored at room temperature for up to 4 days.