Sourdough Rhubarb Cake Recipe
Sourdough rhubarb cake is perfectly moist with a light and tender crumb, thanks to the sourdough discard! Tart rhubarb is folded into a light, buttermilk cake batter that’s baked with a cinnamon sugar and rhubarb topping. It’s the best flavors of summer in a simple dessert.
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Summer is in full bloom, and so is the rhubarb! This sourdough rhubarb cake is moist, tart, and lightly sweet. Sprinkled with a dusting of cinnamon and sugar, rhubarb cake is a perfect way to celebrate a summer birthday or indulge in a sweet treat after dinner.
But that’s not all, the leftovers make the loveliest seasonal coffee cake to enjoy with your morning cup of coffee or tea.
Enjoy this easy recipe and make good use of summer’s first harvest!
What is Rhubarb?
Rhubarb is a long, stalky plant that looks similar to celery. However, the stalks can range in color from deep red to light pink, with some varieties a pale green. Rhubarb plants are one of the first things to grow in the early summer months. These early stalks will be tender and have the most flavor, but you can harvest through the entire summer. Select firm stalks that are 8 to 16 inches long. To harvest, twist the stalk and pull at soil level rather than cutting near the roots. Cut and compost the leaf.
Can you believe that rhubarb is one of the first veggies of the season? While fresh rhubarb is considered a vegetable and has a sour flavor, it’s usually prepared like fruit, with plenty of sugar to balance the tartness of the rhubarb. You may be asking, what does rhubarb taste like in a cake? Upon baking, this unique vegetable becomes tender and juicy and adds a slightly tart flavor that contrasts nicely with the sweetness of the cake itself. The result is a moist cake that sends your tastebuds dancing.
With our love of all things rhubarb, you’ll find plenty of rhubarb recipes here, including rhubarb crumble bars, rhubarb crisp, and mixed berry rhubarb jam.
Why You’ll Love Sourdough Rhubarb Cake
- Sourdough – I love baking with sourdough! Keeping a sourdough starter has so many uses beyond just sourdough bread recipes. The sourdough discard in the cake batter increase in acidity and weakens the gluten, making this cake incredibly tender and light. For this reason, adding sourdough discard is a great way to make muffins, pancakes, and even thicken sauces tastes delicious. With so many ways to use it, be sure to check out these sourdough discard recipes.
- Delicious – Sourdough rhubarb cake has bits of tart rhubarb baked in a tender, sweet cake for the ultimate sourdough discard dessert.
- Quick and easy – I’m a sucker for a great quick and easy sourdough discard recipe and this one is no exception. The reward of this delicious treat far surpasses the minimal amount of effort it takes to create, leaving no reason not to make this cake.
Sourdough Rhubarb Cake Ingredients
Wet Ingredients
- Sourdough discard – Active sourdough starter or sourdough discard will work for this cake.
- Rhubarb – Small pieces of rhubarb can be frozen, just extend the baking time. Don’t let the pieces thaw or you’ll get mushy bits of rhubarb in your cake!
- Butter – Let unsalted butter come to room temperature for easy mixing.
- Sugar – Adds sweetness to the cake, but also creates a tender and moist crumb.
- Eggs – Remove the eggs from the fridge and allow them to come to room temperature. To warm them quickly, place them in a bowl of warm water for 10-15 minutes while you prep the ingredients.
- Vanilla extract – Adds a subtle warmth that makes the cake scrumptious! Use homemade vanilla extract or store-bought.
- Buttermilk – The secret to many light and airy baked goods. The acid in the buttermilk reacts with the baking soda for added lift.
Dry Ingredients
- Flour – All-purpose flour makes a light and tender cake, but has enough strength to hold all of the rhubarb.
- Baking soda – Just a touch of baking soda reacts with the acid in the sourdough starter and buttermilk to leaven the cake.
- Baking powder – Use aluminum free double acting baking powder. It will have two reactions, once when it gets wet as the cake is mixed, and a second when it gets hot in the oven.
- Salt – Adds flavor to the cake.
Topping
- Cinnamon – The spice adds a hint of warm to the cake.
- Sugar – Creates a crispy topping that adds a lovely texture, contrasting the tenderness of the cake.
- Rhubarb – Long stalks of rhubarb enhance the cake’s flavor while showcasing the beautiful colors of the stalk!
How to Make Sourdough Rhubarb Discard Cake
Prep
Preheat the oven to 350°F/177°C with the rack in the middle of the oven.
Line a 9″ square baking pan with parchment paper
First, gather and wash the rhubarb stalks. Trim the ends and discard the leaves. Chop 1 cup of rhubarb into ½ inch pieces and cut the remaining 4 or 5 pieces so that they fit inside the pan diagonally to create a pattern.
In a small bowl, combine 50 g (¼ cup) sugar and 1 tsp cinnamon and set aside.
Mix the Cake Batter
Mixing up this cake is a breeze with a hand mixer, stand mixer, or by hand with a spoon.
In a medium bowl, whisk together 313 g (2 ½ cups) flour, 1 tsp salt, 2 tsp baking powder, and ½ tsp baking soda; set aside.
In a separate large bowl, add 113 g (½ cup) unsalted butter and 100 g (½ cup) sugar and cream with a large spoon until smooth.
Next, add 2 eggs, 1 tsp vanilla extract, and 125 g (½ cup) sourdough discard to the bowl, and whisk until smooth.
Then add the flour mixture to the butter mixture alternately with the buttermilk, beginning and ending with the flour mixture, mix until just combined after each addition. Scrape the sides of the bowl as needed. Do not overmix! It’s okay if there are a few streaks of flour left in the cake mixture.
Gently fold the cut rhubarb chunks into the cake batter.
Why alternate adding the flour mixture with the milk? It all has to do with the butter. The whipped butter and sugar mixture won’t absorb much liquid. If you begin with the liquid, or worse, even add it all, the butter becomes saturated and separates, keeping the liquid on top. Once you add the dry ingredients, they absorb all of the liquid, creating a heavy cake instead of a light and airy cake.
Assemble and Bake the Cake
Pour the cake batter into the prepared cake pan and smooth the top. Sprinkle the cinnamon sugar mixture over the top of the batter. Add the long pieces of rhubarb to the top of the cake in any pattern you like and gently press them into the batter a bit.
Place the cake into the preheated oven and bake for 45 minutes. The cake is done when a toothpick inserted into the middle of the cake comes out clean and the top of the cake springs back.
Place the cake on a wire rack to let the cake cool before cutting for the best texture and flavor.
Serve with a dollop of homemade whipped cream or a scoop of vanilla ice cream.
Like all baked goods, this sourdough rhubarb cake is best the day it’s baked. However, if you do have leftovers, allow the cake to cool completely before placing the cake in an airtight container. Store at room temperature for up to 2 days.
FAQs
Can I Bake With Frozen Rhubarb?
Yes, and I do it all the time. Rhubarb season is so short – I like to harvest some throughout the season and stash it into the freezer. It allows me to enjoy rhubarb desserts year-round!
Add frozen slices of rhubarb to your recipe, but do not let them thaw or they’ll become soft and watery. Because the frozen rhubarb brings the internal temperature of the cake batter down, you’ll need to increase the baking time.
If this is your first time experimenting with rhubarb, welcome to a wide and wonderful world of possibilities! There is no better combination than a perfect tart dessert wrapped in sugary sweetness. I would love to hear what you think, and I wish you a happy summer full of rhubarb cakes!
If You Loved This Recipe, You’ll Love These Other Discard Recipes…
- Sourdough cinnamon and sugar quick bread
- Sourdough zucchini bread – a discard recipe
- The best chocolate zucchini bread recipe
Sourdough Rhubarb Cake Recipe
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Ingredients
Wet Ingredients
- 113 g unsalted butter ½ cup, room temperature
- 100 g sugar ½ cup
- 2 large eggs room temperature
- 1 tsp vanilla extract
- 250 g buttermilk 1 cup
- 125 g sourdough discard ½ cup
Dry Ingredients
- 313 g all-purpose flour 2½ cups
- ½ tsp baking soda
- 2 tsp baking powder
- 1 tsp salt
- 125 g rhubarb 1 cup, chopped
Topping
- 50 g sugar 1/4 cup
- 1 tsp cinnamon
- 6-8 stalks rhubarb stalks
Instructions
Prep
- Preheat the oven to 350°F/177°C with the rack in the middle of the oven.
- Line a 9″ square baking pan with parchment paper
- First, gather and wash the rhubarb stalks. Trim the ends and discard the leaves. Chop 1 cup of rhubarb into ½ inch pieces and cut the remaining pieces so that they fit inside the pan diagonally to create a pattern.
- In a small bowl, combine 50 g (¼ cup) sugar and 1 tsp cinnamon and set aside.
Mix the Cake Batter
- Mixing up this cake is a breeze with a hand mixer, stand mixer, or by hand with a spoon.
- In a medium bowl, whisk together 313 g (2 ½ cups) flour, 1 tsp salt, 2 tsp baking powder, and 1/2 tsp baking soda.
- In a separate large bowl, add 113 g (½ cup) unsalted butter and 100 g (½ cup) sugar and cream with a large spoon until smooth.
- Add 2 eggs, 1 tsp vanilla extract, and 125 g (½ cup) sourdough discard to the bowl, and whisk until smooth.
- Add the flour mixture to butter mixture alternately with the buttermilk, beginning and ending with the flour mixture, mix until just combined after each addition and stopping to scrape the sides of the bowl. Do not over mix! It’s ok if there are a few streak of flour left in the cake mixture.
- Gently fold the cut rhubarb chunks into the cake batter.
Assemble and Bake the Cake
- Pour the cake batter into the prepared cake pan and smooth the top. Sprinkle the cinnamon sugar mixture over the top of the batter. Add the long pieces of rhubarb to the top of the cake in any pattern you like and gently press them into the batter a bit.
- Place the cake into the preheated oven and bake for 45 minutes. The cake is done when a toothpick inserted into the middle of the cake comes out clean and the top of the cake springs back.
- Place the cake on a wire rack to let the cake cool before cutting for the best texture and flavor.
- Serve with a dollop of homemade whipped cream or a scoop of vanilla ice cream.
