This Riesling rhubarb crisp cake has it all: tender white cake, rhubarb-strawberry compote and matching buttercream, a crispy oat crumble, and a fanciful, ruffled finish. It’s the perfect cake to bake when you’re feeling like showing off your cake-baking skills or looking for a weekend project to tackle when you want to spend the day in the kitchen.
Customize Your Cake, Layer by Layer
If there is one thing we know about layer cakes, it’s that it’s okay to gradually work up to incorporating all of these elements at once. Give yourself permission to work at your own skill level and only use the bits and pieces you are comfortable with to make this cake your own.
Don’t have time to make the oat crumble, or the ruffled finish doesn’t fit your design aesthetic? That’s totally okay! Feel free to leave an element out this time or switch up the style of frosting. It’s more about taking the skills and design inspiration to customize your own creation. However, if you want to go all out, we certainly support that too.
When all of the flavors and textures come together, this cake is otherworldly. The earthy tang of rhubarb mixed with sweet strawberries pairs beautifully with crisp Riesling in the summertime. Made with egg whites and a cup-and-a-half of sweet Riesling, the cake itself is light and tender. Serve each slice with a side of leftover rhubarb compote for an extra pop of flavor and color.
Taking inspiration from a baked fruit crisp, we’re adding handfuls of homemade oat crumble between the layers of cake and rhubarb buttercream for an added crunch. Who ever said streusel was just made for topping? Make a double batch and toss leftovers on anything from yogurt to roasted stone fruit to ice cream. (Or just eat it straight from the jar.)
The Frosting This Cake Deserves
What’s an elaborate cake filling without an intricate exterior to match? This grand finale of a cake has equally impressive buttercream details as the mouth-watering flavors inside. Using a pastry bag and a petal-shaped piping tip, rows of overlapping horizontal ruffles encircle the entire cake.
While they may look delicate and, well, complicated, applying different amounts of pressure on the piping bag in conjunction with the petal tip is all it takes to create the elegant, frilled edges. Keeping the rows of ruffles as even as possible will keep the whole cake looking amazing, even if each individual ruffle is not perfect. Not really your style? Switch out the piping tip and explore a variety of other textures to pipe on the cake, or grab an offset spatula and make swoops and swirls for a rustic, homemade look.
Riesling Rhubarb Crisp Cake
Makes 1 (8-inch) layer cake; serves 12 to 16
- For the Riesling cake:
- Butter or nonstick cooking spray, for pan
- 3 1/4 cups (425 grams) cake flour, plus more for the pans
- 1 tablespoon plus 1/2 teaspoon baking powder
- 3/4 teaspoon fine salt
- 1 cup (2 sticks/225 grams) unsalted butter, at room temperature
- 2 cups (400 grams) granulated sugar
- 6 large egg whites
- 1 1/2 cups (360 milliliters) sweet Riesling
- For the rhubarb strawberry compote
- 1 3/4 cups (8 ounces/225 grams) fresh strawberries, hulled and quartered
- 1 cup (4 ounces/115 grams) fresh rhubarb, cut into 1/4-inch (6-millimeter) pieces
- 1/2 cup granulated sugar
- 2 tablespoons fresh lemon juice
- For the buttercream:
- 1 cup (240 milliliter) large egg whites
- 2 cups (400 grams) granulated sugar
- 3 cups (6 sticks/675 grams) unsalted butter, at room temperature
- 1 tablespoon pure vanilla extract
- For the oat crumble:
- 1/2 cup (45 grams) quick-cooking oats
- 1/4 cup (25 grams) sliced almonds
- 1/4 cup (55 grams) firmly packed brown sugar
- 1/4 cup (30 grams) all-purpose flour
- 3 tablespoons unsalted butter, at room temperature
- 2 tablespoons honey
- 1/2 teaspoon ground cinnamon
- 1/4 teaspoon fine salt
- For assembly:Remaining buttercream
- Fresh strawberries for decorating (optional)
Make the Riesling cake:
Arrange 2 racks to divide the oven into thirds and heat to 350°F (175°C). Grease and flour 3 (8-inch or 20-centimeter) round cake pans and set aside.
Sift together the flour, baking powder, and salt and set aside.
In the bowl of a stand mixer fitted with the paddle attachment, beat the butter on medium speed until smooth. Add the sugar and mix on medium-high until the butter is light and fluffy, 3 to 5 minutes. Stop the mixer and scrape down the bowl.
Turn the mixer to medium-low and gradually add the vanilla and egg whites until combined. Stop the mixer and scrape down the bowl. Turn the mixer to low and add the flour mixture in three batches, alternating with the Riesling, beginning and ending with the flour mixture. Mix on medium for no more than 30 seconds after the last streaks of the dry ingredients are combined.
Evenly divide the batter among the prepared pans. Bake for 23 to 25 minutes, or until a toothpick inserted into the center of the cakes comes out clean, switching the cakes between racks halfway through. Let them cool on a wire rack for 10 to 15 minutes before removing the cakes from their pans.
Make the rhubarb strawberry compote:
Combine the strawberries, rhubarb, sugar, and lemon juice in a medium saucepan and cook them over medium-high heat, stirring intermittently with a wooden spoon, until the juices start to bubble.
Reduce the heat to maintain a simmer and cook for 8 to 10 minutes, or until the fruit starts to break down. Remove the pan from the heat and let cool.
Make the buttercream:
Place the egg whites and sugar in the bowl of a stand mixer. Whisk them together by hand to combine.
Fill a medium saucepan with a few inches of water and place it over medium-high heat. Place the mixer bowl on top of the saucepan to create a double boiler. The bottom of the bowl should not touch the water. Whisking intermittently, heat the egg mixture until it registers 145°F to 155°F (63°C to 68°C) on a candy thermometer or is hot to the touch.
Once hot, carefully fit the mixer bowl onto the stand mixer. With the whisk attachment, beat the egg white mixture on high speed for 8 to 10 minutes, until it holds medium-stiff peaks. When done, the outside of the mixer bowl should return to room temperature and no residual heat should be escaping the meringue out of the top of the bowl. Stop the mixer and swap out the whisk attachment for the paddle.
With the mixer on low speed, add the butter, a few tablespoons at a time, and then the vanilla. Once incorporated, turn up the mixer speed to medium-high and beat until the buttercream is silky-smooth, 3 to 5 minutes.
Remove all but 2 cups of the buttercream from the stand mixer bowl. Add 1/2 cup (120 milliliters) of rhubarb compote (reserve the rest for serving) to the mixer and mix until combined.
Make the oat crumble:
Arrange a rack in the middle of the oven and heat to 375°F (190°C). Line a baking sheet with parchment paper.
In a medium bowl, mix together the oats, almonds, brown sugar, flour, butter, honey, cinnamon, and salt with a wooden spoon until combined. The mixture should resemble clumps of sand.
Sprinkle it over the baking sheet and bake, stirring halfway through, for 8 to 10 minutes, or until golden-brown. Let it cool and crumble the mixture into smaller pieces, if necessary.
Assemble the cake:
Once the cakes have completely cooled, level them and choose which layer will be at the bottom. Place it on a cake plate or serving dish.
Spread on 1 cup (240 milliliers) of the rhubarb buttercream with an offset spatula. Sprinkle it with 1/2 to 3/4 cup (50 to 75 grams) of the oat crumble. Top with the next layer of cake and repeat with the buttercream and remaining crumble, finishing with the final layer of cake.
Frost the top and sides cake with the remaining vanilla buttercream. Top with fresh strawberries, if using, and serve with the remaining compote.