Sourdough Strawberry Rhubarb Squares

These Sourdough Strawberry Rhubarb Squares are a taste of summer. This irresistible sourdough dessert is a cross between a cookie and a pie with a gooey rhubarb and strawberry filling and icing to top it off! When the rhubarb and strawberry season is upon you; pull out that extra sourdough discard and make a dessert everyone will love.

sourdough strawberry rhubarb squares

Sourdough Discard

As a sourdough bread lover, I always have my sourdough starter on my counter. As much as I love sourdough bread; I am not a planner. I think about making bread and plans change and my well-fed starter flattens to sourdough discard. This used to feel so wasteful until I discovered sourdough discard recipes. Sourdough discard is so useful! You can make everything from sourdough waffles to sourdough discard desserts.

If you don’t have a sourdough starter yet don’t worry! You can check out my SOURDOUGH DISCARD BLOG to get t started. You do not have to wait days on end to use your sourdough discard as you do for a sourdough bread recipe that needs an active bubbly starter. Discard recipes like this one you can make with a sourdough discard that isn’t suitable for rising bread.

Rhubarb Season

I live on the East Coast and rhubarb is the most prolific plant I know. Almost everyone has it growing in their garden, yard, or ditch. Once you plant it there is no need to water it or take care of it. This stuff just GROWS and my neighbors have told me no matter how many times they try to get rid of it: it just keeps coming back. I love rhubarb. I am down for any strawberry rhubarb recipe. Whether it is a pie, tart, or square: sign me up! It is always the first thing to sprout in my garden letting me know spring is officially here, and summer is on its way. Rhubarb can be made into everything from barbeque sauce to desserts. I’m not a huge fan of it raw but cook it up and pair it with some strawberries and I am a happy camper.

What You’ll Need

  • Flour
  • Butter
  • Sourdough discard
  • Sugar
  • Eggs
  • Salt
  • Vanilla
  • Rhubarb
  • Strawberry Jam
  • Cornstarch
  • Powder Sugar
  • Cream/Milk

Strawberry Goodness

In this recipe, you will see I used strawberry jam. I live in a cold climate so more often than not rhubarb season and strawberry season don’t cross paths. I either need to preserve my strawberries in a jam or chop and freeze my rhubarb. Usually, I do both. If you have fresh strawberries on hand you can thinly slice them, toss in flour and add an extra layer on top of your gooey filling. This is the perfect sourdough dessert to welcome Spring or Summer. It is so fresh and yummy but not too sweet. I love using up my sourdough discard to give a slight tang and something about it makes the texture irresistible. It is not quite a cookie and not really a cake. Sourdough discard dessert is a treat in our house.

sourdough discard dessert

Let’s get started…

First, you will want your butter softened at room temperature. With a wire whisk/whip attachment cream together your butter and sugar. Once that is fluffy and a lighter color, add in your eggs. When you have that combined switch out this wire whisk for your paddle and add in your sourdough discard flour, salt, and vanilla. Turn up your speed and get the dough fluffy. The dough should be very thick and sticky.

Line a 9×13 glass pan with parchment paper, scoop out half the dough, and spread evenly. If you’re having a hard time spreading it out with a spoon. Just go ahead and wet your hands a bit and spread it out that way. Flatten it out evenly and move over to the stove to start your filling.

The nice thing about sourdough discard desserts is you don’t have to wait or ferment them, just simply add it in!

The Perfect Strawberry Rhubarb Filling

For your filling, you will want to chop your rhubarb into small pieces. Set aside. In a medium-sized pot add your water, sugar, cornstarch, and jam. Bring to a high heat constantly whisking and then remove from the hot burner. Add in your freshly chopped rhubarb and give a few stirs to prevent it from sticking to the pot. Once the mixture has cooled a bit and thickened, pour over the batter in the pan.

chopping rhubarb


If you want to add fresh strawberries now is the time to do it! Just chop or thinly slice and toss in a few tbsps of flour until evenly coated. This helps the water in the strawberries not leak out and mess up your other layers.

Take the rest of the batter and spread it on top of your filling layer. I like to have mine in large pieces with a few cracks to let the filling peak through.

Bake at 325 for 80 mins. You may find it takes less time or more depending on your oven so at the 1-hour mark check it every 5-10 mins so it does not burn. You want the entire top to be an even golden brown. When finished baking remove and let cool.

While your squares are baking you can mix up your icing in a small bowl. Combine icing sugar and cream and whisk until there are no lumps. Let your strawberry rhubarb squares cool completely before adding icing to your sourdough discard dessert.

Sourdough dessert recipe strawberry rhubabr squares with strawberry

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sourdough strawberry rhubarb squares

Sourdough Strawberry Rhubarb Squares

Sourdough discard dessert with strawberry rhubarb filling.
Prep Time 20 minutes
Cook Time 1 hour 20 minutes
Course Dessert
Cuisine American, canadian
Servings 16 squares


  • 1 Stand Mixer
  • 1 Glass Pan 9×13


Sourdough Square

  • 1 cup Butter softened
  • 1.5 cups Sugar
  • 3 Cups Flour
  • 3 Eggs
  • 1/2 cup Sourdough Discard
  • 1 tsp Salt
  • 1 tsp Vanilla Extract

Rhubarb sauce

  • 1/2 cup water
  • 1/2 cup Sugar
  • 3-4 tbsp Strawberry jam
  • 1/2 tsp Vanilla Extract
  • 3 Tbsp cornstarch
  • 2 cups Rhubarb chopped


  • 1/2 cup Powdered sugar
  • 3 tbsp Cream


  • Preheat oven to 325

Square Base

  • Cream together butter and sugar with wire whisk attachment
  • Add eggs, flour, sourdough discard, salt and vanilla. Mix well for 5 mins on mediem speed.
  • Line a 9×13 glass baking pan with parchement paper.
  • Pour in half the batter and smooth flat for bottom half of squares. Because this dough can be quite thick and sticky to deal with if you need to use your hands to get a nice even base just wet them first so the dough doesn't stick to you!


  • Chop rhubarb into small pieces.
  • In a pot combine water, sugar, cornstartch and jam. whisking constantly Bring to a boil and remove from heat. Stir in rhubarb and set aside.

Put it all together!

  • Pour your fillling onto base batter and spread evenly
  • With clean damp hands flaten and spread the rest of your batter on to the filling layer to create the top layer of your square.
  • Bake at 325 for 80 miuntes


  • Allow squares to completely cool
  • Scoop icing into plastic bag and snip the corner. Pipe in zig zags across squares .
Keyword Sourdough, sourdough dessert, sourdough discard, strawberry rhubarb

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