High Altitude Macadamia Nut Cake with Salted Penuche Frosting

A high altitude recipe for macadamia nut cake, made of two layers of brown butter macadamia cake, frosted with sweet penuche frosting and finished with a sprinkling of flaky salt. This cozy cake is rich and nutty, salty and sweet, full of flavor, and perfect for the colder fall and winter months.

You might also love this maple macadamia nut biscotti, hazelnut shortbread cookies, one layer coffee and walnut cake.

Why You’ll Love This Recipe

Easy to Make. The cake is easy to make, with standard pantry ingredients. You don’t even need a mixer to make the cake batter.

Soft and Moist. The texture of this cake is just so good. It’s a little dense, but so soft, moist, and rich with macadamia nuts and brown butter.

High Altitude Tested. I develop all the recipes on my site for Denver’s altitude of 5,280 feet.

What is Penuche Frosting?

Penuche frosting, pronounced “pen-oo-chee”, is a very sweet, cooked brown sugar frosting. It’s almost fudge like, with flavor notes of caramel, toffee or butterscotch. Penuche frosting isn’t fluffy like buttercream, and is a bit more challenging for frosting a layer cake. It has a soft texture, but it sets and crusts over as it’s exposed to air.

When I taste this frosting, I instantly think of my grandma. She had a big sweet tooth when I was a kid, and loved making cake with penuche frosting whenever she came to visit. Since it is so sweet, a sprinkling of flaky salt on top helps to balance the sweetness.

This is not a frosting I’d recommend for those who are beginners with making layer cakes. If you want to use this penuche frosting recipe, but you’re not experienced in assembling layer cakes, I’d recommend making the macadamia nut cake as a one layer cake, and then just spreading the frosting on top of the cake, which is a much easier option.

See the recipe card at the end of the post for the full ingredients list and instructions.

Ingredients

Macadamia Nut Cake

• Unsalted Butter. Adds moisture and richness. Browning the butter first adds a nutty depth of flavor that’s delicious with the macadamia nuts and penuche frosting.
• 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.
• Vanilla Extract. Flavor.
• Whole Milk + Sour Cream. 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 nuts.
• Baking Powder. Leavening agent, so the cake rises when it bakes.
• Macadamia Nuts. Finely chop the macadamia nuts before adding them to the cake batter for a nutty, flavorful cake.

Penuche Frosting

• Butter. I use unsalted butter, but you can use salted and just reduce the extra salt in the recipe.
• Brown Sugar. You can use light or dark brown sugar, which will add a caramel flavor to the frosting.
• Milk. Use whole milk for the richest flavor.
• Powdered Sugar. Thickens the frosting and adds more sweetness.
• Vanilla Extract. Flavor.
• Salt. Balances the sweetness.

Instructions

Cake

• Preheat the oven to 350 F, and position a rack in the center of the oven. Spray the bottoms of two 6-inch cake pans 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.

• Add the brown sugar, granulated sugar, eggs, vanilla, milk, and sour cream to the brown butter and whisk until combined.
• 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 macadamia nuts.

• Divide the batter between the pans, and bake for about 28-32 minutes, until the tops spring back when gently touched, or a toothpick or cake tester comes out clean. Cool the cakes in the pans for 20 minutes (the top of the cake will settle and flatten as the cake cools).
• After 20 minutes, run a knife around the edges, and turn the cakes out onto a piece of plastic wrap. Wrap the cake layers individually in plastic wrap, and cool completely. Note: The reason for wrapping the cakes is that this cake recipe is a bit more dense, and since it’s butter based, it develops a crust while baking. Wrapping the cake while warm allows the steam to soften the crust and keeps the cake very moist.

Frosting

• In a saucepan, melt the butter over medium low heat. Add the brown sugar and cook, stirring constantly with a spatula, until it begins to boil, then boil for 2 minutes. The mixture should reach 236 degrees Fahrenheit.
• Stir in the milk, return to a boil, then remove from the heat.

• Pour the mixture into a bowl, and let cool to room temperature, stirring occasionally.
• Add the powdered sugar, vanilla and salt, and use an electric mixer to beat the frosting for several minutes until smooth and thick.
• Note that this frosting does not have the consistency of a fluffy buttercream, and since it’s thinner, it can be a little trickier for spreading onto a layer cake. If it seems too thin, you can beat in more powdered sugar, 1/4 cup at a time. If it gets too cool and thick, beat in hot water, 1 tablespoon at a time.

• Spread a thin layer of frosting on top of one of the cooled cake layers, then place the second cake layer on top. Frost all over with a thin crumb coat of frosting. Chill in the refrigerator for 30 minutes to let the frosting set and firm up, then add more frosting if you like.
• Note that since this frosting is so sweet, I frosted my cake pretty thinly, with just a crumb coat around the sides, and a little more swirled on top of the cake.

Recipe Variations

8-inch Layer Cake. For a two layer 8-inch cake, double the cake recipe, but you don’t need to double the frosting.

Sheet Cake. For a one layer cake, bake the cake in a 9 inch square baking pan. Or you can double the cake recipe and bake it in a 9×13 inch pan.

Troubleshooting Penuche Frosting

Too Thick and Stiff. If your frosting is too thick, stiff and hard to spread, then it either cooled for too long, or you added too much powdered sugar. If this happens, add some hot water, one tablespoon at a time, to thin it out.

Too Thin and Slippery. If your frosting is too thin, soft and slippery and you’re having a hard time assembling your layer cake, then you didn’t add enough powdered sugar, or you simply need to let it cool for longer. Cover the frosting with plastic wrap and refrigerate it for a few minutes to help it thicken up. You can also refrigerate the cake once you have the crumb coat on, to help set and firm up the frosting in between the layers.

Be sure to read all of my BAKING FAQs where I discuss ingredients, substitutions and common questions with cake making, so that you can be successful in your own baking! I also suggest reading these comprehensive posts on making Perfect American Buttercream, How to Stack, Fill, Crumb Coat and Frost Layer Cakes and How to Use Piping Bags.

Frequently Asked Questions

If I don’t want to make the penuche frosting, what buttercream recipe would you recommend?

For a less sweet frosting, my go to for cakes is my perfect American buttercream recipe.

How should I store the leftover cake?

Store leftover macadamia nut cake in an airtight container at room temperature for up to 3 days.

Should I use salted or unsalted macadamia nuts?

Typically, I bake with unsalted nuts, but macadamia nuts are harder to find unsalted, so this recipe does use salted nuts. Since the nuts are salted, I slightly reduced the salt in the cake batter.

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