High Altitude Rhubarb Layer Cake with Candied Rhubarb Curls
Three layers of moist vanilla cake, filled with sweet rhubarb curd and rhubarb buttercream, topped with the prettiest candied rhubarb curls.
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 Whisk Attachment
- 8-inch cake pans (x3)
Ingredients
Cake
- 1 ½ cups granulated sugar
- 3 ¼ cups cake flour, spooned and leveled
- 3 tsp baking powder
- 1 tsp coarse Kosher salt (if using table salt, use half the amount)
- 2 large eggs
- 2 large egg whites
- 1 ½ cups whole buttermilk, room temperature
- ½ cup unsalted butter, melted
- ½ cup vegetable oil
- 1 tbsp vanilla extract
Buttercream
- 2 cups unsalted butter, softened to room temperature
- ½ cup rhubarb curd (or rhubarb jam)
- 4 cups powdered sugar
- 1 tbsp meringue powder, optional
- ¼ tsp coarse Kosher salt (if using table salt, use half the amount)
- 2 tsp vanilla extract
Filling
- ¾ cup rhubarb curd (or rhubarb jam)
Rhubarb Curls
- 1 cup water
- 1 cup sugar
- 2-6 stalks fresh rhubarb, depending on their size
Instructions
Cake
- Preheat the oven to 350F and spray the bottoms of three 8-inch cake pans with non-stick spray.
- In a large bowl, sift together the sugar, cake flour, baking powder and salt. Use a whisk to combine the dry ingredients well.
- In another large bowl, whisk together the eggs, egg whites, buttermilk, melted butter, oil and vanilla extract until smooth.
- Add the dry ingredients to the wet, and whisk until combined and smooth, about 10-15 seconds. Divide the batter between the cake pans. Tap a few times against the counter to pop any large air bubbles.
- Bake the cakes for about 21-25 minutes, or until a cake tester or a toothpick comes out clean, and the tops spring back when lightly touched.
- Set the pans on a wire rack, cover them loosely with a clean kitchen towel, and cool completely before frosting. When ready to frost and assemble the cake, remove the cakes from the pans.
- If making the cakes in advance, let them cool until warm, then turn the cakes out and wrap each layer individually in plastic wrap. Store the wrapped cake layers at room temperature overnight, until you're ready to frost the cake. Or, freeze the wrapped cakes for up to 3-6 months.
Buttercream
- In the bowl of your stand mixer fitted with the whisk attachment, beat the butter for 1 minute until smooth. Beat in the rhubarb curd.
- With the mixer running on low, add the powdered sugar by spoonfuls, the meringue powder and the salt, mixing until thick and combined. Add the vanilla.
- Increase speed to medium and whip for 4-5 minutes (#6 on a Kitchen Aid mixer), scraping the bowl down several times, until light and fluffy. Turn the speed down to "stir" and mix for 1 minute to get rid of any large air bubbles.
Assembly
- Unwrap the cooled cakes. Use a sharp (non-serrated knife) to split each layer so you have a total of 6 layers.
- Place one cake layer on a cake board or cake pedestal, with the split side facing up. Spread 1/4 cup of rhubarb curd over the cake, not quite to the edges. Place another cake layer on top of the rhubarb filling, with the split side facing down. This way, the open crumb of the split cakes can soak up the rhubarb curd. Now add a layer of buttercream.
- Repeat the above step with more layers of cake, rhubarb curd and buttercream. You should have 6 layers of cake, alternating with 3 layers of rhubarb curd and 3 layers of buttercream.Note: The layers should alternate like this from the bottom up: cake, rhubarb curd, cake, buttercream, cake, rhubarb curd, cake, buttercream, cake, rhubarb curd, cake, buttercream.
- Frost the cake all over with a thin crumb coat of buttercream. Refrigerate for 30 minutes to chill the crumb coat, then frost all over with a pretty, swirly coat of buttercream.
Rhubarb Curls
- Combine the water and sugar in a medium-sized saucepan. Bring to a boil to dissolve the sugar, then remove from the heat. Let cool for 5 minutes while you prep the rhubarb.
- To cut the rhubarb ribbons, lay a rhubarb stalk down on a cutting board. Using a sharp paring knife, gently wedge the knife in at one end, so that it pierces just the outer skin. Glide the knife away from you down the stalk, so that you slice off a long strip of the outer skin. Work your way around the stalk, slicing off as many strips as you can.Note: A vegetable peeler does not work well for this project, as it peels off shredded, fibrousy strips that are way too thin. Use a paring knife for strips that are thin enough to be flexible, but not so thin that they fall apart.Note: No need to throw out the unused portion of the rhubarb stalks, since you're only using the outer skin. Just chop up what's left, place it in a freezer bag, and freeze to use in jam or a pie.
- Place the rhubarb ribbons in the simple syrup, and let them soak for 5 minutes.
- Preheat the oven to 200F, and line a large baking sheet with parchment paper or a nonstick baking mat so the candied rhubarb doesn't stick.
- Remove the rhubarb ribbons from the simple syrup.For large, loopy curls, arrange the ribbons in big curls.For ringlets, lay the ribbons out flat in a straight line, which you will shape into ringlets after they dry for a bit.
- Dry the candied rhubarb for about 60-90 minutes, until it feels pretty dry.Note: If you're making ringlets, then let the strips dry for about 30 minutes, then wrap the warm rhubarb ribbons around a wooden chopstick, place them back on the baking sheet, and continue to dry in the oven.
- Line a container with a piece of parchment paper or wax paper. Gently transfer the rhubarb curls to the container. When they're warm from the oven, they can be brittle and break easily if you're not gentle. Keep them loosely covered for up to 1 day, until you're ready to decorate your cake.
- Since the candied rhubarb will soften as it sits on the moist cake, I'd suggest waiting to place them on your cake until you're ready to present the cake.
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