Sourdough Rhubarb Snack Cake

Do you grow rhubarb? One of my childhood memories is of a wild and unruly garden our family tried and mostly failed at tending. Rhubarb, however grew plentifully. Mom would take these beautiful stalks of rhubarb, chop them, coat the rhubarb pieces in sugar and transform them into the perfect rhubarb pie (no strawberries…just sweet/tart rhubarb). Ever since, I’ve loved rhubarb with its sweet and tart flavor combination. This sourdough rhubarb snack cake reminds me of the rhubarb pie I grew up eating. Nothing but rhubarb and sweet sugar to give flavor to this cake. The rhubarb melts into the tender cake and sweet crumb topping and makes a delicious snack or dessert on a spring or summer day. The next time you see rhubarb at your local grocery or farmer’s market, pick some up! Add this sourdough rhubarb snack cake to your list to make this summer.

What is the Difference Between Green and Red Rhubarb?

What is the difference between green and red rhubarb? I asked myself this question as we tried growing rhubarb ourselves last year and the stalks mostly came out green with just a hint of red. Apparently, there is not much difference! The flavor of red and green rhubarb is the same. It’s just the color that looks different. The photos from this rhubarb snack cake were taken with rhubarb straight from our garden, which just happened to be more on the green side. Aesthetically, if you prefer the look of red rhubarb choose that when you pick up the rhubarb for this cake. It will taste delicious, no matter the color!

Using Sourdough Discard in Sourdough Rhubarb Snack Cake

A word of warning: not all sourdough discard is created equal. The age of the discard makes a difference. I prefer using a “fresh” discard that is only a day or two old (at the most). My family didn’t even know there was sourdough in this recipe because the discard I used came straight from the jar – right before I fed my starter again. Some of my family members like the tang in sourdough bread but not baked goods. Discard that has been sitting in the fridge for a week or two gives a lot more “tang” to this cake. You can also use bubbly sourdough starter for less sourdough flavor but all the sourdough benefits.

How to Make Sourdough Rhubarb Snack Cake

Mix up the Batter

If you’ve been around for any length of time, you know that I love using the least number of bowls possible in baking (fewer bowls = fewer dishes to wash). While this recipe isn’t exactly a one-bowl recipe, the number of bowls can be reduced with these tips. Use a small bowl to mix together the rhubarb, sugar and lemon zest. Set it aside. To a medium-sized bowl, beat together the butter, sugar and lemon zest until light and fluffy. Add the egg, sourdough discard, sour cream and vanilla and beat until light and fluffy. For the dry mixture: add the flour right on top of the center of the wet mixture (don’t mix it in yet…this is the one-bowl method). Add the baking powder and salt on top of the FLOUR. Use a fork to fluff the baking powder and salt into the flour to combine it just a bit. Then use the mixer to combine the dry ingredients with the wet until just combined. Spread this batter in an 8 by 8, parchment-lined pan, top it with the rhubarb and then mix up the crumb topping in the bowl the rhubarb mixture was in–see what I did there? Saved you from washing dishes!

Use a Parchment Sling

Do yourself a favor and use a parchment sling for this snack cake. Non-stick parchment paper makes this easy to lift out of your baking pan and cut into beautiful pieces. I like to lay parchment paper over the top of the pan, cut the corners out of each piece and then press it into the pan. You can watch a video of this process here. I used to think lining a pan with parchment paper was overrated. Nope! Now, I don’t bake without it! My favorite parchment paper is this one from Costco, though it looks like you can snag it on Amazon too. It holds up great for baking crusty sourdough and for all the cookie bars too.

Crumb Topping for Sourdough Rhubarb Cake

Don’t even think about making this cake without the crumb topping. The sweet crumbs nestled in between tart rhubarb is what gives this cake such a unique and delicious flavor. The crumb topping is quick to toss together and gives a deeper flavor by using brown sugar. For quick cleanup, mix up the crumb topping in the same bowl the rhubarb mixture sat in. You don’t even need to wash it out first.

Baking the Cake

Stick the finished cake in a preheated 350 degree oven. Once the cake is baking, check on it after about 50 minutes by sticking a toothpick or thin knife into the center of the cake. If no wet batter streaks remain, the cake is finished baking. Most ovens vary in temperature, so it’s important to look for the signs of readiness instead of going purely off the written recipe time. Let the cake cool and enjoy!

Frequently Asked Questions

Can I add strawberries to this cake to make a strawberry rhubarb sourdough snack cake?

I have never done this, but I think it would taste good (maybe a tad bit sweeter). I would chop ripe strawberries and replace them for about 1/3 of the rhubarb in the rhubarb mixture.

What can I substitute for sour cream in this recipe?

If you don’t have sour cream on hand, I like to replace this with the same amount of Greek Yogurt. Plain yogurt would work in a pinch.

What is 100% hydration sourdough discard?

100% hydration means an equal weight of water and flour added to a small amount of sourdough. Sourdough can be kept at different hydrations for different purposes. Most sourdough recipes will call for 100% hydration, meaning the sourdough starter was fed with equal weights of flour and water. If your starter is not kept at 100% hydration, you may need to increase the flour in the recipe (for higher hydration–more liquid sourdough) or decrease the flour for lower hydration (stiffer sourdough).

Sourdough Rhubarb Snack Cake

Sweet and tart, tender and delicious, this sourdough rhubarb snack cake is full of summer flavors perfect for a summer party or to enjoy on spring day.
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Prep Time 20 minutes
Cook Time 55 minutes
Total Time 1 hour 15 minutes
Course Dessert, Snack
Cuisine American
Servings 16 slices


Rhubarb Mixture

  • 1 1/2-2 cups rhubarb, chopped into 1 inch pieces
  • cup white sugar
  • ½ Tablespoon lemon juice fresh squeezed is best, save lemon to zest for cake

Sourdough Snack Cake

  • ¼ cup unsalted butter, softened
  • cup granulated sugar
  • ½ teaspoon lemon zest
  • 1 large egg
  • cup sourdough discard 100% hydration, see recipe notes
  • 2 Tablespoons sour cream or greek yogurt
  • ½ teaspoon vanilla extract
  • ¾ cup all purpose flour
  • 1 teaspoon baking powder
  • ½ teaspoon salt

Crumb Topping

  • 2 Tablespoons unsalted butter melted
  • 2 Tablespoons packed brown sugar
  • ½ cup all purpose flour
  • pinch of salt
  • sprinkle of cinnamon


  • Preheat oven to 350 degrees Fahrenheit.
  • Chop rhubarb into small, 1 inch pieces and toss into a small bowl. Add 1/3 cup sugar and lemon zest. Stir to combine and set aside.
  • To a medium sized bowl, beat together butter, sugar and lemon zest until light and fluffy. Add the egg and beat again until fully incorporated. Add the sourdough discard, sour cream and vanilla extract. Beat together until incorporated.
  • To the middle of the mixture (or in a separate small bowl), add the flour, baking powder and salt. Lightly fluff the baking powder and salt into the flour with a fork (if mixing in a bowl, add it to the wet mixture now) and mix until just combined.
  • Scoop the batter into the prepared pan and gently spread into an even layer using an offset spatula or the back of a spoon. Pour the prepared rhubarb mixture over the cake batter, creating an even layer as best you can.
  • Stir together the crumb mixture: melt the butter and add the brown sugar, flour, salt and sprinkle of cinnamon. Once it comes together, use your fingers to spread chunks of crumb topping evenly over the rhubarb layer.
  • Bake in preheated oven for 50-60 minutes. The cake is finished when a toothpick is inserted into the cake and comes out clean–no wet cake batter. Cool completely and then remove the cake (using your parchment sling) and cut into pieces to serve. Enjoy!


Sourdough Discard: Not all sourdough discard is created equal. Discard that has been sitting in the fridge for a month will be more sour than discard sitting for a day or two. Using older discard can alter or deepen the sourdough flavor. If you don’t want much sourdough flavor and are making this recipe to use up discard, use a “newer” or less-sour discard. If you want to taste the sourdough flavor, choose a discard that has been in your refrigerator for awhile.
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  1. Can’t wait to try this recipe! My tradition for baking rhubarb pies came from your grandma! As a child, I, too, had wild stalks of rhubarb in our yard. And when the yard didn’t produce well, we always found it at the store and made delicious pies and rhubarb compote. Yum!! Thanks for the memories, and sharing this new recipe! 🥧😋