A high altitude recipe for a one layer coffee and walnut cake. The cake is rich and nutty with brown butter and chopped walnuts, with a wonderful coffee flavor from instant espresso powder. Frosted with fluffy coffee buttercream, this cozy coffee walnut cake will be one you’ll want to make over and over during the colder fall and winter months.
You might also love these high altitude recipes for French apple walnut tart, maple walnut cake, and maple walnut shortbread.
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Why You’ll Love This Recipe
Just One Layer. I love the effortless simplicity of a one layer cake, sometimes referred to as a snack cake. See the recipe variations section below if you want to find out how to turn this coffee walnut cake into a layer cake, if that’s what you prefer.
So Much Coffee Flavor. The flavor and aroma of freshly brewed coffee is one of my favorite things, and it’s so good with the nuttiness of the walnuts and brown butter. I didn’t add any spices to this cake, to really let the coffee and walnuts shine.
Dense and Nutty. Since this cake is butter based, the texture dense, moist and nutty with plenty of chopped walnuts.
High Altitude Tested. I develop all of the recipes on my site for Denver’s altitude of 5,280 feet, so mountain bakers can bake with confidence.
See the recipe card at the end of the post for the full ingredients list and instructions.
Ingredients
Cake
- Butter. To add the most incredible flavor to this cake, don’t skip the step of browning the butter first.
- Sugar. Light brown sugar with a touch of white sugar adds sweetness and moisture to the cake, as well as a hint of molasses flavor.
- Eggs. Gives the cake structure and helps the batter to hold together.
- Espresso Powder. You’ll need instant espresso powder to add the coffee flavor to both the cake and the buttercream.
- Vanilla Extract. Flavor.
- Whole Milk. Adds fat and moisture for a moist, tender cake.
- Flour. All-purpose flour gives the cake structure and strength.
- Salt. Balances the sweetness and enhances the flavor of the walnuts.
- Baking Powder. Leavening agent, so the cake rises when it bakes.
- Walnuts. Finely chop the walnuts before adding them to the cake batter for a nutty, flavorful cake.
Buttercream
- Butter. I use unsalted butter, but you can use salted and just omit the extra salt in the recipe.
- Vanilla Extract. Flavor.
- Powdered Sugar. Sweetens and thickens the buttercream.
- Salt. Balances the sweetness.
- Meringue Powder. Adds stability.
- Cream + Espresso Powder. To extract the most flavor from the espresso powder, dissolve it in a splash of cream first, then add to the buttercream.
Instructions
Cake
- Preheat the oven to 350 F, and position a rack in the center of the oven. Line a 9-inch square baking dish with parchment paper, or spray it with non-stick baking spray.
- In a saucepan, melt the butter over medium heat. Continue to cook the butter until nutty, golden brown milk solids form at the bottom of the pan. This process might take about 10 minutes. First the butter will hiss and splatter as the water evaporates, then as it quiets down, a layer of foam will form on top of the butter. This means the butter is done. Immediately remove from the heat, and scrape the butter, including the brown milk solids, into a large bowl. Let cool for 10 minutes.
- Whisk the espresso powder into the butter, then add the brown sugar, granulated sugar, eggs, vanilla and milk, and whisk until combined. If some of the butter solidifies into small pieces, this is nothing to worry about.
- In a separate bowl, sift together the flour, salt and baking powder, then whisk until everything is evenly distributed.
- Add the dry ingredients to the wet, whisking until moistened, then fold in the chopped walnuts.
- Pour the batter into the prepared pan, and bake for about 30-32 minutes, until the top springs back when gently touched, or a toothpick or cake tester comes out clean. Set the pan on a wire rack, covered with a clean kitchen towel, and cool completely before frosting.
Buttercream
- In the bowl of your stand mixer fitted with the paddle attachment, beat the butter and vanilla extract for 1 minute, until smooth.
- Add the powdered sugar, meringue powder and salt, mixing on low until combined. In a small bowl, whisk together the cream and espresso powder until the coffee is dissolved, then add it to the buttercream. Whip the buttercream on medium high speed for 4-5 minutes, until very light and fluffy, scraping the bowl down several times while mixing. Turn the speed down to “stir” and mix for 1 more minute.
- Spread the buttercream onto the cooled cake, swirling it with an offset spatula. Cut the cake into 16 squares (for small servings) or 9 squares (for large servings), and top each square of cake with a walnut.
Recipe Variations
- For a two-layer 6-inch cake, bake the cake batter in two 6-inch round cake pans for about 28-32 minutes. See this maple walnut cake for decorating ideas.
- For a larger 8-inch cake, double the cake recipe, and bake in two 8-inch round cake pans. Double the buttercream as well.
- For a 9×13 inch sheet cake, double the cake recipe, and increase the buttercream by 1 1/2 times.
Be sure to read all of my BAKING FAQs where I discuss ingredients, substitutions and common baking questions, so that you can be successful in your own baking!
Frequently Asked Questions
Where do I find espresso powder?
I use Medaglia D’Oro Instant Espresso Coffee, which I buy at my local Kroger. It has a great flavor, and I use it often in baked goods.
Can I use brewed coffee in the cake batter instead of espresso powder?
While I haven’t tried this substitution, it would likely work fine. I would suggest replacing the milk with strong coffee that’s been cooled to room temperature. You do need the espresso powder in the buttercream, though.
Can I use pecans instead of walnuts?
For sure! If you want a coffee pecan cake instead of a coffee walnut cake, go right ahead.
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High Altitude One Layer Coffee and Walnut Cake
All recipes on Curly Girl Kitchen are developed for high altitude at 5,280 feet. See FAQs for adjusting to higher or lower elevations.
Equipment
- Stand Mixer with Paddle Attachment
Ingredients
Cake
- ¾ cup unsalted butter
- 1 ½ tbsp instant espresso powder
- 1 cup light brown sugar, lightly packed
- 2 tbsp granulated sugar
- 2 large eggs, room temperature
- 1 tsp vanilla extract
- 1 cup whole milk, room temperature
- 1 ½ cups all-purpose flour, fluffed, spooned and leveled
- ½ tsp coarse Kosher salt (if using table salt, use half the amount)
- ¾ tsp baking powder
- ½ cup walnuts, finely chopped
Buttercream
- ¾ cup unsalted butter
- 1 tsp vanilla extract
- 1 ½ cups powdered sugar
- ⅛ tsp coarse Kosher salt (if using table salt, use half the amount)
- ½ tbsp meringue powder
- 1 tbsp heavy whipping cream
- 1 tbsp instant espresso powder
- walnut halves, for decorating
Instructions
Cake
- Preheat the oven to 350 F, and position a rack in the center of the oven. Line a 9-inch square baking dish with parchment paper, or spray it with non-stick baking spray.
- In a saucepan, melt the butter over medium heat. Continue to cook the butter until nutty, golden brown milk solids form at the bottom of the pan. This process might take about 10 minutes. First the butter will hiss and splatter as the water evaporates, then as it quiets down, a layer of foam will form on top of the butter. This means the butter is done. Immediately remove from the heat, and scrape the butter, including the brown milk solids, into a large bowl. Let cool for 10 minutes.
- Whisk the espresso powder into the butter, then add the brown sugar, granulated sugar, eggs, vanilla and milk, and whisk until combined. If some of the butter solidifies into small pieces, this is nothing to worry about.
- In a separate bowl, sift together the flour, salt and baking powder, then whisk until everything is evenly distributed.
- Add the dry ingredients to the wet, whisking until moistened, then fold in the chopped walnuts.
- Pour the batter into the prepared pan, and bake for about 30-32 minutes, until the top springs back when gently touched, or a toothpick or cake tester comes out clean. Set the pan on a wire rack, covered with a clean kitchen towel, and cool completely before frosting.
Buttercream
- In the bowl of your stand mixer fitted with the paddle attachment, beat the butter and vanilla extract for 1 minute, until smooth.
- Add the powdered sugar, meringue powder and salt, mixing on low until combined. In a small bowl, whisk together the cream and espresso powder until the coffee is dissolved, then add it to the buttercream. Whip the buttercream on medium high speed for 4-5 minutes, until very light and fluffy, scraping the bowl down several times while mixing. Turn the speed down to "stir" and mix for 1 more minute.
- Spread the buttercream onto the cooled cake, swirling it with an offset spatula. Cut the cake into 16 squares (for small servings) or 9 squares for large servings, and top each square of cake with a walnut.
Notes
- For a two-layer 6-inch cake, bake the cake batter in two 6-inch cake pans.
- For a larger 8-inch cake, double the cake recipe, and bake in two 8-inch cake pans. Double the buttercream.
What adjustments should I make to this recipe for NON high altitude baking? I am in SC. This cake sound delicious!
Renee, I have some helpful info on adjusting recipes for various altitudes in my FAQs: https://curlygirlkitchen.com/baking-faqs/